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Chapter 7

Indices — Exercise 7

Class - 9 ML Aggarwal Understanding ICSE Mathematics



Exercise 7

Question 1

(i) (−24332)−35\Big(-\dfrac{243}{32}\Big)^{-\dfrac{3}{5}}

(ii) (52364)−23\Big(5\dfrac{23}{64}\Big)^{-\dfrac{2}{3}}

Answer

Given,

⇒(−24332)−35⇒(−3525)−35⇒[(−32)5]−35⇒(−32)−5×35⇒(−32)−3⇒(−23)3⇒−827.\Rightarrow \Big(-\dfrac{243}{32}\Big)^{-\dfrac{3}{5}}\\[1em] \Rightarrow \Big(-\dfrac{3^5}{2^5}\Big)^{-\dfrac{3}{5}}\\[1em] \Rightarrow \Big[\Big(-\dfrac{3}{2}\Big)^5\Big]^{-\dfrac{3}{5}}\\[1em] \Rightarrow \Big(-\dfrac{3}{2}\Big)^{-\dfrac{5 \times 3}{5}}\\[1em] \Rightarrow \Big(-\dfrac{3}{2}\Big)^{-3}\\[1em] \Rightarrow \Big(-\dfrac{2}{3}\Big)^3\\[1em] \Rightarrow -\dfrac{8}{27}.

Hence, (−24332)−35=−827\Big(-\dfrac{243}{32}\Big)^{-\dfrac{3}{5}} = -\dfrac{8}{27}.

(ii) Given,

⇒(52364)−23⇒(34364)−23⇒(7343)−23⇒[(74)3]−23⇒(74)−2×33⇒(74)−2⇒(47)2⇒1649.\Rightarrow \Big(5\dfrac{23}{64}\Big)^{-\dfrac{2}{3}}\\[1em] \Rightarrow \Big(\dfrac{343}{64}\Big)^{-\dfrac{2}{3}}\\[1em] \Rightarrow \Big(\dfrac{7^3}{4^3}\Big)^{-\dfrac{2}{3}}\\[1em] \Rightarrow \Big[\Big(\dfrac{7}{4}\Big)^3\Big]^{-\dfrac{2}{3}}\\[1em] \Rightarrow \Big(\dfrac{7}{4}\Big)^{-\dfrac{2 \times 3}{3}}\\[1em] \Rightarrow \Big(\dfrac{7}{4}\Big)^{-2}\\[1em] \Rightarrow \Big(\dfrac{4}{7}\Big)^2\\[1em] \Rightarrow \dfrac{16}{49}.

Hence, (52364)−23=1649\Big(5\dfrac{23}{64}\Big)^{-\dfrac{2}{3}} = \dfrac{16}{49}.

Question 2(i)

Simplify the following:

(2a-3b2)3

Answer

Given,

⇒ (2a-3b2)3 = (2)3(a-3)3(b2)3

= 8a-9b6.

Hence, (2a-3b2)3 = 8a-9b6.

Question 2(ii)

Simplify the following:

a−1+b−1(ab)−1\dfrac{a^{-1} + b^{-1}}{(ab)^{-1}}

Answer

Given,

⇒a−1+b−1(ab)−1=(a−1+b−1)×1(ab)−1=(1a+1b)×ab=(a+bab)×ab=a+b.\Rightarrow \dfrac{a^{-1} + b^{-1}}{(ab)^{-1}} = (a^{-1} + b^{-1}) \times \dfrac{1}{(ab)^{-1}} \\[1em] = \Big(\dfrac{1}{a} + \dfrac{1}{b}\Big) \times ab \\[1em] = \Big(\dfrac{a + b}{ab}\Big) \times ab \\[1em] = a + b.

Hence, a−1+b−1(ab)−1\dfrac{a^{-1} + b^{-1}}{(ab)^{-1}} = a + b.

Question 3(i)

Simplify the following:

x−1y−1x−1+y−1\dfrac{x^{-1}y^{-1}}{x^{-1} + y^{-1}}

Answer

Given,

⇒x−1y−1x−1+y−1=(xy)−1×1x−1+y−1=1xy×11x+1y=1xy×1x+yxy=1xy×xyx+y=1x+y.\Rightarrow \dfrac{x^{-1}y^{-1}}{x^{-1} + y^{-1}} = (xy)^{-1} \times \dfrac{1}{x^{-1} + y^{-1}} \\[1em] = \dfrac{1}{xy} \times \dfrac{1}{\dfrac{1}{x} + \dfrac{1}{y}} = \dfrac{1}{xy} \times \dfrac{1}{\dfrac{x + y}{xy}} \\[1em] = \dfrac{1}{xy} \times \dfrac{xy}{x + y} = \dfrac{1}{x + y}.

Hence, x−1y−1x−1+y−1=1x+y\dfrac{x^{-1}y^{-1}}{x^{-1} + y^{-1}} = \dfrac{1}{x + y}

Question 3(ii)

Simplify the following:

(4×107)(6×10−5)8×1010\dfrac{(4 \times 10^7)(6 \times 10^{-5})}{8 \times 10^{10}}

Answer

Given,

⇒(4×107)(6×10−5)8×1010=4×6×107×10−58×1010=24×107+(−5)8×1010=24×1028×1010=3×102×10−10=3×102+(−10)=3×10−8.\Rightarrow \dfrac{(4 \times 10^7)(6 \times 10^{-5})}{8 \times 10^{10}} = \dfrac{4 \times 6 \times 10^7 \times 10^{-5}}{8 \times 10^{10}} \\[1em] = \dfrac{24 \times 10^{7 + (-5)}}{8 \times 10^{10}} = \dfrac{24 \times 10^2}{8 \times 10^{10}} \\[1em] = 3 \times 10^2 \times 10^{-10} = 3 \times 10^{2 + (-10)} \\[1em] = 3 \times 10^{-8}.

Hence, (4×107)(6×10−5)8×1010=3×10−8.\dfrac{(4 \times 10^7)(6 \times 10^{-5})}{8 \times 10^{10}} = 3 \times 10^{-8}.

Question 4(i)

Simplify the following:

3ab−1+2ba−1\dfrac{3a}{b^{-1}} + \dfrac{2b}{a^{-1}}

Answer

Given,

⇒3ab−1+2ba−1=3a1b+2b1a=3ab+2ab=5ab.\Rightarrow \dfrac{3a}{b^{-1}} + \dfrac{2b}{a^{-1}} = \dfrac{3a}{\dfrac{1}{b}} + \dfrac{2b}{\dfrac{1}{a}}\\[1em] = 3ab + 2ab = 5ab.

Hence, 3ab−1+2ba−1\dfrac{3a}{b^{-1}} + \dfrac{2b}{a^{-1}} = 5ab.

Question 4(ii)

Simplify the following:

50 × 4-1 + 8138^{\dfrac{1}{3}}

Answer

Given,

⇒50×4−1+813=1×4−1+(23)13=1×14+2=1+84=94=214.\Rightarrow 5^0 \times 4^{-1} + 8^{\dfrac{1}{3}} = 1 \times 4^{-1} + (2^3)^{\dfrac{1}{3}} \\[1em] = 1 \times \dfrac{1}{4} + 2 \\[1em] = \dfrac{1 + 8}{4} \\[1em] = \dfrac{9}{4} \\[1em] = 2\dfrac{1}{4}.

Hence, 50×4−1+813=2145^0 \times 4^{-1} + 8^{\dfrac{1}{3}} = 2\dfrac{1}{4}.

Question 5(i)

Simplify the following:

(8125)−13\Big(\dfrac{8}{125}\Big)^{-\dfrac{1}{3}}

Answer

Given,

⇒(8125)−13=(1258)13=(5323)13=53×1323×13=52=212.\Rightarrow \Big(\dfrac{8}{125}\Big)^{-\dfrac{1}{3}} = \Big(\dfrac{125}{8}\Big)^{\dfrac{1}{3}} \\[1em] = \Big(\dfrac{5^3}{2^3}\Big)^{\dfrac{1}{3}} = \dfrac{5^{3 \times \dfrac{1}{3}}}{2^{3 \times \dfrac{1}{3}}}\\[1em] = \dfrac{5}{2} = 2\dfrac{1}{2}.

Hence, (8125)−13=212.\Big(\dfrac{8}{125}\Big)^{-\dfrac{1}{3}} = 2\dfrac{1}{2}.

Question 5(ii)

Simplify the following:

(0.027)−13(0.027)^{-\dfrac{1}{3}}

Answer

Given,

⇒(0.027)−13=[(0.3)3]−13=(0.3)−1=10.3=103=313.\Rightarrow (0.027)^{-\dfrac{1}{3}} = [(0.3)^3]^{-\dfrac{1}{3}} \\[1em] = (0.3)^{-1} = \dfrac{1}{0.3} \\[1em] = \dfrac{10}{3} = 3\dfrac{1}{3}. \\[1em]

Hence,(0.027)−13=313(0.027)^{-\dfrac{1}{3}} = 3\dfrac{1}{3}.

Question 6(i)

Simplify the following:

(−127)−23\Big(-\dfrac{1}{27}\Big)^{-\dfrac{2}{3}}

Answer

Given,

⇒(−127)−23=(−27)23=(−3)3×23=(−3)2=9.\Rightarrow \Big(-\dfrac{1}{27}\Big)^{-\dfrac{2}{3}} = (-27)^{\dfrac{2}{3}} \\[1em] = (-3)^{3 \times \dfrac{2}{3}} = (-3)^2 \\[1em] = 9.

Hence, (−127)−23\Big(-\dfrac{1}{27}\Big)^{-\dfrac{2}{3}} = 9.

Question 6(ii)

Simplify the following:

(64)−23÷(9)−32(64)^{-\dfrac{2}{3}} ÷ (9)^{-\dfrac{3}{2}}

Answer

Given,

⇒(64)−23÷(9)−32=(164)23÷(19)32=(126)23÷(132)32=(1)2326×23÷(1)3232×32=124÷133=124×33=2716=11116.\Rightarrow (64)^{-\dfrac{2}{3}} ÷ (9)^{-\dfrac{3}{2}} = \Big(\dfrac{1}{64}\Big)^{\dfrac{2}{3}} ÷ \Big(\dfrac{1}{9}\Big)^{\dfrac{3}{2}} \\[1em] = \Big(\dfrac{1}{2^6}\Big)^{\dfrac{2}{3}} ÷ \Big(\dfrac{1}{3^2}\Big)^{\dfrac{3}{2}} \\[1em] = \dfrac{(1)^{\dfrac{2}{3}}}{2^{6 \times \dfrac{2}{3}}} ÷ \dfrac{(1)^{\dfrac{3}{2}}}{3^{2 \times \dfrac{3}{2}}} \\[1em] = \dfrac{1}{2^4} ÷ \dfrac{1}{3^3} \\[1em] = \dfrac{1}{2^4} \times 3^3 \\[1em] = \dfrac{27}{16} = 1\dfrac{11}{16}.

Hence, (64)−23÷(9)−32=11116(64)^{-\dfrac{2}{3}} ÷ (9)^{-\dfrac{3}{2}} = 1\dfrac{11}{16}.

Question 7(i)

Simplify the following:

(27)2n3×(8)−n6(18)−n2\dfrac{(27)^{\dfrac{2n}{3}} \times (8)^{-\dfrac{n}{6}}}{(18)^{-\dfrac{n}{2}}}

Answer

Given,

⇒(27)2n3×(8)−n6(18)−n2=(33)2n3×(23)−n6(2×32)−n2=32n×(2)−n2(2)−n2×(32)−n2=32n3−n=32n13n=32n×3n=3(2n+n)=33n.\Rightarrow \dfrac{(27)^{\dfrac{2n}{3}} \times (8)^{-\dfrac{n}{6}}}{(18)^{-\dfrac{n}{2}}} \\[1em] = \dfrac{(3^3)^{\dfrac{2n}{3}} \times (2^3)^{-\dfrac{n}{6}}}{(2 \times 3^2)^{-\dfrac{n}{2}}} \\[1em] = \dfrac{3^{2n} \times (2)^{-\dfrac{n}{2}}}{(2)^{-\dfrac{n}{2}} \times (3^2)^{-\dfrac{n}{2}}} \\[1em] = \dfrac{3^{2n}}{3^{-n}} = \dfrac{3^{2n}}{\dfrac{1}{3^n}} \\[1em] = 3^{2n} \times 3^n \\[1em] = 3^{(2n + n)} = 3^{3n}. \\[1em]

Hence, (27)2n3×(8)−n6(18)−n2=33n\dfrac{(27)^{\dfrac{2n}{3}} \times (8)^{-\dfrac{n}{6}}}{(18)^{-\dfrac{n}{2}}} = 3^{3n}.

Question 7(ii)

Simplify the following:

5.(25)n+1−25.(5)2n5.(5)2n+3−(25)n+1\dfrac{5.(25)^{n + 1} - 25.(5)^{2n}}{5.(5)^{2n + 3} - (25)^{n + 1}}

Answer

Given,

⇒5.(25)n+1−25.(5)2n5.(5)2n+3−(25)n+1=5.(52)n+1−(52)(5)2n5.(5)2n+3−(52)n+1=5.52n+2−52+2n52n+4−52n+2=52n+3−52n+252n+4−52n+2=52n.53−52n.5252n.54−52n.52=52n(53−52)52n(54−52)=125−25625−25=100600=16.\Rightarrow \dfrac{5.(25)^{n + 1} - 25.(5)^{2n}}{5.(5)^{2n + 3} - (25)^{n + 1}} \\[1em] = \dfrac{5.(5^2)^{n + 1} - (5^2)(5)^{2n}}{5.(5)^{2n + 3} - (5^2)^{n + 1}} \\[1em] = \dfrac{5.5^{2n + 2} - 5^{2 + 2n}}{5^{2n + 4} - 5^{2n + 2}} \\[1em] = \dfrac{5^{2n + 3} - 5^{2n + 2}}{5^{2n + 4} - 5^{2n + 2}} \\[1em] = \dfrac{5^{2n}.5^3 - 5^{2n}.5^2}{5^{2n}.5^4 - 5^{2n}.5^2} \\[1em] = \dfrac{5^{2n}(5^3 - 5^2)}{5^{2n}(5^4 - 5^2)} \\[1em] = \dfrac{125 - 25}{625 - 25} \\[1em] = \dfrac{100}{600} = \dfrac{1}{6}.

Hence, 5.(25)n+1−25.(5)2n5.(5)2n+3−(25)n+1=16\dfrac{5.(25)^{n + 1} - 25.(5)^{2n}}{5.(5)^{2n + 3} - (25)^{n + 1}} = \dfrac{1}{6}.

Question 8(i)

Simplify the following:

[8−43÷2−2]12\Big[8^{-\dfrac{4}{3}} ÷ 2^{-2}\Big]^{\dfrac{1}{2}}

Answer

Given,

⇒[8−43÷2−2]12=[(18)43÷(12)2]12=[(123)43÷(12)2]12=[123×43÷(122)]12=[124×22]12=(122)12=12.\Rightarrow \Big[8^{-\dfrac{4}{3}} ÷ 2^{-2}\Big]^{\dfrac{1}{2}} = \Big[\Big(\dfrac{1}{8}\Big)^{\frac{4}{3}} ÷ \Big(\dfrac{1}{2}\Big)^2 \Big]^{\dfrac{1}{2}} \\[1em] = \Big[\Big(\dfrac{1}{2^3}\Big)^{\dfrac{4}{3}} ÷ \Big(\dfrac{1}{2}\Big)^2 \Big]^{\dfrac{1}{2}} \\[1em] = \Big[\dfrac{1}{2^{3 \times \dfrac{4}{3}}} ÷ \Big(\dfrac{1}{2^2}\Big)\Big]^{\dfrac{1}{2}} \\[1em] = \Big[\dfrac{1}{2^4} \times 2^2\Big]^{\dfrac{1}{2}} \\[1em] = \Big(\dfrac{1}{2^2}\Big)^{\dfrac{1}{2}} \\[1em] = \dfrac{1}{2}.

Hence, [8−43÷2−2]12=12\Big[8^{-\dfrac{4}{3}} ÷ 2^{-2}\Big]^{\dfrac{1}{2}} = \dfrac{1}{2}.

Question 8(ii)

Simplify the following:

(278)23−(14)−2+50\Big(\dfrac{27}{8}\Big)^{\dfrac{2}{3}} - \Big(\dfrac{1}{4}\Big)^{-2} + 5^0

Answer

Given,

⇒(278)23−(14)−2+50=(3323)23−42+1=33×2323×23−16+1=3222−15=94−15=9−604=−514=−1234.\Rightarrow \Big(\dfrac{27}{8}\Big)^{\dfrac{2}{3}} - \Big(\dfrac{1}{4}\Big)^{-2} + 5^0 = \Big(\dfrac{3^3}{2^3}\Big)^{\dfrac{2}{3}} - 4^2 + 1 \\[1em] = \dfrac{3^{3 \times \dfrac{2}{3}}}{2^{3 \times \dfrac{2}{3}}} - 16 + 1 \\[1em] = \dfrac{3^2}{2^2} - 15 \\[1em] = \dfrac{9}{4} - 15 \\[1em] = \dfrac{9 - 60}{4} \\[1em] = -\dfrac{51}{4} = -12\dfrac{3}{4}.

Hence, (278)23−(14)−2+50=−1234.\Big(\dfrac{27}{8}\Big)^{\dfrac{2}{3}} - \Big(\dfrac{1}{4}\Big)^{-2} + 5^0 = -12\dfrac{3}{4}.

Question 9(i)

Simplify the following:

(3x2)−3×(x9)23(3x^2)^{-3} \times (x^9)^{\dfrac{2}{3}}

Answer

Given,

⇒(3x2)−3×(x9)23=(13x2)3×[(x3)3]23=127x6×(x3)3×23=127x6×x6=127.\Rightarrow (3x^2)^{-3} \times (x^9)^{\dfrac{2}{3}} = \Big(\dfrac{1}{3x^2}\Big)^3 \times [(x^3)^3]^{\dfrac{2}{3}} \\[1em] = \dfrac{1}{27x^6} \times (x^3)^{3 \times \dfrac{2}{3}} \\[1em] = \dfrac{1}{27x^6} \times x^6 = \dfrac{1}{27}.\\[1em]

Hence, (3x2)−3×(x9)23=127.(3x^2)^{-3} \times (x^9)^{\dfrac{2}{3}}= \dfrac{1}{27}.

Question 9(ii)

Simplify the following:

(8x4)13÷x13(8x^4)^{\dfrac{1}{3}} ÷ x^{\dfrac{1}{3}}

Answer

Given,

⇒(8x4)13÷x13=(8)13(x4)13×1(x)13=(23)13.(x)43.(x)−13=2.(x)43−13=2.(x)33=2x.\Rightarrow (8x^4)^{\dfrac{1}{3}} ÷ x^{\dfrac{1}{3}} = (8)^{\dfrac{1}{3}} (x^4)^{\dfrac{1}{3}} \times \dfrac{1}{(x)^{\dfrac{1}{3}}} \\[1em] = (2^3)^{\dfrac{1}{3}}.(x)^{\dfrac{4}{3}}.(x)^{-\dfrac{1}{3}} \\[1em] = 2.(x)^{\dfrac{4}{3} - \dfrac{1}{3}} = 2.(x)^{\dfrac{3}{3}} = 2x.

Hence, (8x4)13÷x13(8x^4)^{\dfrac{1}{3}} ÷ x^{\dfrac{1}{3}} = 2x.

Question 10(i)

Simplify the following:

(32)0+3−4×36+(13)−2(3^2)^0 + 3^{-4} \times 3^6 + \Big(\dfrac{1}{3}\Big)^{-2}

Answer

Given,

⇒(32)0+3−4×36+(13)−2=90+134×36+(3)2=1+134×36+32=1+32+32=1+9+9=19.\Rightarrow (3^2)^0 + 3^{-4} \times 3^6 + \Big(\dfrac{1}{3}\Big)^{-2} \\[1em] = 9^0 + \dfrac{1}{3^4} \times 3^6 + (3)^2 \\[1em] = 1 + \dfrac{1}{3^4} \times 3^6 + 3^2 \\[1em] = 1 + 3^2 + 3^2 \\[1em] = 1 + 9 + 9 = 19.

Hence, (32)0+3−4×36÷(13)−2(3^2)^0 + 3^{-4} \times 3^6 ÷ \Big(\dfrac{1}{3}\Big)^{-2} = 19.

Question 10(ii)

Simplify the following:

(9)52−3.(5)0−(181)−12(9)^{\dfrac{5}{2}} - 3.(5)^0 - \Big(\dfrac{1}{81}\Big)^{-\dfrac{1}{2}}

Answer

Given,

⇒(32)52−3.1−(192)−12=32×52−3−(92)12=35−3−9=243−12=231.\Rightarrow (3^2)^{\dfrac{5}{2}} - 3.1 - \Big(\dfrac{1}{9^2}\Big)^{-\dfrac{1}{2}} \\[1em] = 3^{2 \times \dfrac{5}{2}} - 3 - (9^2)^{\dfrac{1}{2}} \\[1em] = 3^5 - 3 - 9 \\[1em] = 243 - 12 \\[1em] = 231.

Hence, (9)52−3.(5)0−(181)−12(9)^{\dfrac{5}{2}} - 3.(5)^0 - \Big(\dfrac{1}{81}\Big)^{-\dfrac{1}{2}} = 231.

Question 11(i)

Simplify the following:

1634+2(12)−1(3)016^{\dfrac{3}{4}} + 2\Big(\dfrac{1}{2}\Big)^{-1}(3)^0

Answer

Given,

⇒1634+2(12)−1(3)0=(24)34+2.(2)1.1=23+4=8+4=12.\Rightarrow 16^{\dfrac{3}{4}} + 2\Big(\dfrac{1}{2}\Big)^{-1}(3)^0 = (2^4)^{\dfrac{3}{4}} + 2.(2)^1 .1 \\[1em] = 2^3 + 4 = 8 + 4 = 12.

Hence, 1634+2(12)−1(3)016^{\dfrac{3}{4}} + 2\Big(\dfrac{1}{2}\Big)^{-1}(3)^0 = 12.

Question 11(ii)

Simplify the following:

(81)34−(132)−25+(8)13(12)−1(2)0(81)^{\dfrac{3}{4}} - \Big(\dfrac{1}{32}\Big)^{-\dfrac{2}{5}} + (8)^{\dfrac{1}{3}}\Big(\dfrac{1}{2}\Big)^{-1}(2)^0

Answer

Given,

⇒(81)34−(132)−25+(8)13(12)−1(2)0=(34)34−(32)25+(23)13(2)1.1=33−(25)25+2.2=27−22+4=27−4+4=27.\Rightarrow (81)^{\dfrac{3}{4}} - \Big(\dfrac{1}{32}\Big)^{-\dfrac{2}{5}} + (8)^{\dfrac{1}{3}}\Big(\dfrac{1}{2}\Big)^{-1}(2)^0 = (3^4)^{\dfrac{3}{4}} - (32)^{\dfrac{2}{5}} + (2^3)^{\dfrac{1}{3}}(2)^1.1 \\[1em] = 3^3 - (2^5)^{\dfrac{2}{5}} + 2.2 \\[1em] = 27 - 2^2 + 4 \\[1em] = 27 - 4 + 4 = 27.

Hence, (81)34−(132)−25+(8)13(12)−1(2)0(81)^{\dfrac{3}{4}} - \Big(\dfrac{1}{32}\Big)^{-\dfrac{2}{5}} + (8)^{\dfrac{1}{3}}\Big(\dfrac{1}{2}\Big)^{-1}(2)^0 = 27.

Question 12(i)

Simplify the following:

(64125)−23÷1(256625)14+(25643)0\Big(\dfrac{64}{125}\Big)^{-\dfrac{2}{3}} ÷ \dfrac{1}{\Big(\dfrac{256}{625}\Big)^{\dfrac{1}{4}}} + \Big(\dfrac{\sqrt{25}}{\sqrt[3]{64}}\Big)^0

Answer

Given,

⇒(64125)−23÷1(256625)14+(25643)0=(12564)23×(256625)14+1=[(54)3]23×[(45)4]14+1=(54)2×45+1=54+1=94=214.\Rightarrow \Big(\dfrac{64}{125}\Big)^{-\dfrac{2}{3}} ÷ \dfrac{1}{\Big(\dfrac{256}{625}\Big)^{\dfrac{1}{4}}} + \Big(\dfrac{\sqrt{25}}{\sqrt[3]{64}}\Big)^0 \\[1em] = \Big(\dfrac{125}{64}\Big)^{\dfrac{2}{3}} \times \Big(\dfrac{256}{625}\Big)^{\dfrac{1}{4}} + 1 \\[1em] = \Big[\Big(\dfrac{5}{4}\Big)^3\Big]^{\dfrac{2}{3}} \times \Big[\Big(\dfrac{4}{5}\Big)^4\Big]^{\dfrac{1}{4}} + 1 \\[1em] = \Big(\dfrac{5}{4}\Big)^2 \times \dfrac{4}{5} + 1 \\[1em] = \dfrac{5}{4} + 1 \\[1em] = \dfrac{9}{4} = 2\dfrac{1}{4}.

Hence, (64125)−23÷1(256625)14+(25643)0=214\Big(\dfrac{64}{125}\Big)^{-\dfrac{2}{3}} ÷ \dfrac{1}{\Big(\dfrac{256}{625}\Big)^{\dfrac{1}{4}}} + \Big(\dfrac{\sqrt{25}}{\sqrt[3]{64}}\Big)^0 = 2\dfrac{1}{4}

Question 12(ii)

Simplify the following:

5n+3−6×5n+19×5n−22×5n\dfrac{5^{n + 3} - 6 \times 5^{n + 1}}{9 \times 5^n - 2^2 \times 5^n}

Answer

Given,

⇒5n+3−6×5n+19×5n−22×5n=5n.53−6.5n.515n(9−22)=5n.(53−30)5n(9−4)=125−305=955=19.\Rightarrow \dfrac{5^{n + 3} - 6 \times 5^{n + 1}}{9 \times 5^n - 2^2 \times 5^n} = \dfrac{5^n.5^3 - 6.5^n.5^1}{5^n(9 - 2^2)} \\[1em] = \dfrac{5^n.(5^3 - 30)}{5^n(9 - 4)} \\[1em] = \dfrac{125 - 30}{5} \\[1em] = \dfrac{95}{5} = 19.

Hence, 5n+3−6×5n+19×5n−22×5n\dfrac{5^{n + 3} - 6 \times 5^{n + 1}}{9 \times 5^n - 2^2 \times 5^n} = 19.

Question 13(i)

Simplify the following:

[(64)23.2−2÷80]−12\Big[(64)^{\dfrac{2}{3}}.2^{-2} ÷ 8^0\Big]^{-\dfrac{1}{2}}

Answer

Given,

⇒[(64)23.2−2÷80]−12=[[(4)3]23×(12)2÷1]−12=[(42)×(14)]−12=[16×14]−12=[4]−12=(14)12=12=12.\Rightarrow \Big[(64)^{\dfrac{2}{3}}.2^{-2} ÷ 8^0\Big]^{-\dfrac{1}{2}} = \Big[[(4)^3]^{\dfrac{2}{3}} \times \Big(\dfrac{1}{2}\Big)^2 ÷ 1 \Big]^{-\dfrac{1}{2}} \\[1em] = \Big[(4^2) \times \Big(\dfrac{1}{4}\Big)\Big]^{-\dfrac{1}{2}} \\[1em] = \Big[16 \times \dfrac{1}{4}\Big]^{-\dfrac{1}{2}} \\[1em] = [4]^{-\dfrac{1}{2}} \\[1em] = \Big(\dfrac{1}{4}\Big)^{\dfrac{1}{2}} = \dfrac{1}{2} \\[1em] = \dfrac{1}{2}.

Hence, [(64)−23.2−2÷80]−12=12\Big[(64)^{-\dfrac{2}{3}}.2^{-2} ÷ 8^0\Big]^{-\dfrac{1}{2}} = \dfrac{1}{2}.

Question 13(ii)

Simplify the following:

3n×9n+1÷(3n−1×9n−1)3^n \times 9^{n + 1} ÷ (3^{n - 1} \times 9^{n - 1})

Answer

Given,

⇒3n×9n+1÷(3n−1×9n−1)=3n×9n+1×13n−1×9n−1=3n×9n.913n.3−1×9n.9−1=93−1×9−1=9×3×9=243.\Rightarrow 3^n \times 9^{n + 1} ÷ (3^{n - 1} \times 9^{n - 1}) \\[1em] = 3^n \times 9^{n + 1} \times \dfrac{1}{3^{n - 1} \times 9^{n - 1}} \\[1em] = \dfrac{3^n \times 9^n.9^1}{3^n.3^{-1} \times 9^n.9^{-1}} \\[1em] = \dfrac{9}{3^{-1} \times 9^{-1}} \\[1em] = 9 \times 3 \times 9 \\[1em] = 243.

Hence, 3n×9n+1÷(3n−1×9n−1)3^n \times 9^{n + 1} ÷ (3^{n - 1} \times 9^{n - 1}) = 243.

Question 14(i)

Simplify the following:

22×2564643−(12)−2\dfrac{\sqrt{2^2} \times \sqrt[4]{256}}{\sqrt[3]{64}} - \Big(\dfrac{1}{2}\Big)^{-2}

Answer

Given,

⇒22×2564643−(12)−2⇒22×284263−(2)2⇒(22)12×(28)14(26)13−4⇒(2)2×12×(2)8×14(2)6×13−4⇒2×2222−4⇒2−4⇒−2.\Rightarrow \dfrac{\sqrt{2^2} \times \sqrt[4]{256}}{\sqrt[3]{64}} - \Big(\dfrac{1}{2}\Big)^{-2} \\[1em] \Rightarrow \dfrac{\sqrt{2^2} \times \sqrt[4]{2^8}}{\sqrt[3]{2^6}} - (2)^{2} \\[1em] \Rightarrow \dfrac{(2^2)^{\dfrac{1}{2}} \times (2^8)^{\dfrac{1}{4}}}{(2^6)^{\dfrac{1}{3}}} - 4 \\[1em] \Rightarrow \dfrac{(2)^{2 \times \dfrac{1}{2}} \times (2)^{8 \times \dfrac{1}{4}}}{(2)^{6 \times \dfrac{1}{3}}} - 4 \\[1em] \Rightarrow \dfrac{2 \times 2^2}{2^2} - 4 \\[1em] \Rightarrow 2 - 4 \\[1em] \Rightarrow -2.

Hence, 22×2564643−(12)−2\dfrac{\sqrt{2^2} \times \sqrt[4]{256}}{\sqrt[3]{64}} - \Big(\dfrac{1}{2}\Big)^{-2} = -2.

Question 14(ii)

Simplify the following:

3−67×4−37×937×26722+20+2−2\dfrac{3^{-\dfrac{6}{7}} \times 4^{-\dfrac{3}{7}} \times 9^{\dfrac{3}{7}} \times 2^{\dfrac{6}{7}}}{2^2 + 2^0 + 2^{-2}}

Answer

Given,

⇒3−67×4−37×937×26722+20+2−2⇒3−67×(22)−37×(32)37×2674+1+(12)2⇒3−67×(2)−67×(3)67×2674+1+(14)⇒3−67+67×(2)−67+67(16+4+14)⇒30×20214⇒1214⇒421.\Rightarrow \dfrac{3^{-\dfrac{6}{7}} \times 4^{-\dfrac{3}{7}} \times 9^{\dfrac{3}{7}} \times 2^{\dfrac{6}{7}}}{2^2 + 2^0 + 2^{-2}} \\[1em] \Rightarrow \dfrac{3^{-\dfrac{6}{7}} \times (2^2)^{-\dfrac{3}{7}} \times (3^2)^{\dfrac{3}{7}} \times 2^{\dfrac{6}{7}}}{4 + 1 + \Big(\dfrac{1}{2}\Big)^{2}} \\[1em] \Rightarrow \dfrac{3^{-\dfrac{6}{7}} \times (2)^{-\dfrac{6}{7}} \times (3)^{\dfrac{6}{7}} \times 2^{\dfrac{6}{7}}}{4 + 1 + \Big(\dfrac{1}{4}\Big)} \\[1em] \Rightarrow \dfrac{3^{-\dfrac{6}{7} + \dfrac{6}{7}} \times (2)^{-\dfrac{6}{7} + \dfrac{6}{7}}}{\Big(\dfrac{16 + 4 + 1}{4}\Big)} \\[1em] \Rightarrow \dfrac{3^0 \times 2^0}{\dfrac{21}{4}} \\[1em] \Rightarrow \dfrac{1}{\dfrac{21}{4}} \\[1em] \Rightarrow \dfrac{4}{21}.

Hence, 3−67×4−37×937×26722+20+2−2=421\dfrac{3^{-\dfrac{6}{7}} \times 4^{-\dfrac{3}{7}} \times 9^{\dfrac{3}{7}} \times 2^{\dfrac{6}{7}}}{2^2 + 2^0 + 2^{-2}} = \dfrac{4}{21}.

Question 15(i)

Simplify the following:

(32)25×(4)−12×(8)132−2÷(64)−13\dfrac{(32)^{\dfrac{2}{5}} \times (4)^{-\dfrac{1}{2}} \times (8)^{\dfrac{1}{3}}}{2^{-2} ÷ (64)^{-\dfrac{1}{3}}}

Answer

Given,

⇒(32)25×(4)−12×(8)132−2÷(64)−13⇒(25)25×(22)−12×(23)132−2÷(26)−13⇒22×2−1×212−2÷2−2⇒22−1+12−22−2⇒221=22=4.\Rightarrow \dfrac{(32)^{\dfrac{2}{5}} \times (4)^{-\dfrac{1}{2}} \times (8)^{\dfrac{1}{3}}}{2^{-2} ÷ (64)^{-\dfrac{1}{3}}} \\[1em] \Rightarrow \dfrac{(2^5)^{\dfrac{2}{5}} \times (2^2)^{-\dfrac{1}{2}} \times (2^3)^{\dfrac{1}{3}}}{2^{-2} ÷ (2^6)^{-\dfrac{1}{3}}} \\[1em] \Rightarrow \dfrac{2^2 \times 2^{-1} \times 2^1}{2^{-2} ÷ 2^{-2}} \\[1em] \Rightarrow \dfrac{2^{2 - 1 + 1}}{\dfrac{2^{-2}}{2^{-2}}} \\[1em] \Rightarrow \dfrac{2^2}{1} = 2^2 = 4.

Hence, (32)25×(4)−12×(8)132−2÷(64)−13\dfrac{(32)^{\dfrac{2}{5}} \times (4)^{-\dfrac{1}{2}} \times (8)^{\dfrac{1}{3}}}{2^{-2} ÷ (64)^{-\dfrac{1}{3}}} = 4.

Question 15(ii)

Simplify the following:

52(x+6)×(25)−7+2x(125)2x\dfrac{5^{2(x + 6)} \times (25)^{-7 + 2x}}{(125)^{2x}}

Answer

Given,

⇒52(x+6)×(25)−7+2x(125)2x⇒52x+12×(52)−7+2x(53)2x⇒52x+12×5−14+4x56x⇒52x+12+(−14+4x)56x⇒56x−2.5−6x⇒56x−2+(−6x)⇒5−2=152=125.\Rightarrow \dfrac{5^{2(x + 6)} \times (25)^{-7 + 2x}}{(125)^{2x}} \\[1em] \Rightarrow \dfrac{5^{2x + 12} \times (5^2)^{-7 + 2x}}{(5^3)^{2x}} \\[1em] \Rightarrow \dfrac{5^{2x + 12} \times 5^{-14 + 4x}}{5^{6x}} \\[1em] \Rightarrow \dfrac{5^{2x + 12 + (-14 + 4x)}}{5^{6x}} \\[1em] \Rightarrow 5^{6x - 2}.5^{-6x} \\[1em] \Rightarrow 5^{6x - 2 + (-6x)} \\[1em] \Rightarrow 5^{-2} = \dfrac{1}{5^2} = \dfrac{1}{25}.

Hence, 52(x+6)×(25)−7+2x(125)2x=125\dfrac{5^{2(x + 6)} \times (25)^{-7 + 2x}}{(125)^{2x}} = \dfrac{1}{25}.

Question 16(i)

Simplify the following:

72n+3−(49)n+2((343)n+1)23\dfrac{7^{2n + 3} - (49)^{n + 2}}{((343)^{n + 1})^{\dfrac{2}{3}}}

Answer

Given,

⇒72n+3−(49)n+2((343)n+1)23⇒72n+3−(72)n+2((73)n+1)23⇒72n+3−72n+473×(n+1)×23⇒72n.73−72n.7472(n+1)⇒343.72n−2401.72n72n+2⇒72n(343−2401)72n.72⇒−205849=−42.\Rightarrow \dfrac{7^{2n + 3} - (49)^{n + 2}}{((343)^{n + 1})^{\dfrac{2}{3}}} \\[1em] \Rightarrow \dfrac{7^{2n + 3} - (7^2)^{n + 2}}{((7^3)^{n + 1})^{\dfrac{2}{3}}} \\[1em] \Rightarrow \dfrac{7^{2n + 3} - 7^{2n + 4}}{7^{3 \times (n + 1) \times \dfrac{2}{3}}} \\[1em] \Rightarrow \dfrac{7^{2n}.7^3 - 7^{2n}.7^{4}}{7^{2(n + 1)}} \\[1em] \Rightarrow \dfrac{343.7^{2n} - 2401.7^{2n}}{7^{2n + 2}} \\[1em] \Rightarrow \dfrac{7^{2n}(343 - 2401)}{7^{2n}.7^2} \\[1em] \Rightarrow \dfrac{-2058}{49} = -42.

Hence, 72n+3−(49)n+2((343)n+1)23\dfrac{7^{2n + 3} - (49)^{n + 2}}{((343)^{n + 1})^{\dfrac{2}{3}}} = -42.

Question 16(ii)

Simplify the following:

(27)43+(32)0.8+(0.8)−1(27)^{\dfrac{4}{3}} + (32)^{0.8} + (0.8)^{-1}

Answer

Given,

⇒(27)43+(32)0.8+(0.8)−1⇒(33)43+(25)810+(10.8)1⇒(3)3×43+(2)5×810+(108)⇒(3)4+24+54⇒81+16+54⇒97+54⇒388+54⇒3934⇒98.25\Rightarrow (27)^{\dfrac{4}{3}} + (32)^{0.8} + (0.8)^{-1} \\[1em] \Rightarrow (3^3)^{\dfrac{4}{3}} + (2^5)^{\dfrac{8}{10}} + \Big(\dfrac{1}{0.8}\Big)^{1} \\[1em] \Rightarrow (3)^{3 \times \dfrac{4}{3}} + (2)^{5 \times \dfrac{8}{10}} + \Big(\dfrac{10}{8}\Big) \\[1em] \Rightarrow (3)^4 + 2^4 + \dfrac{5}{4} \\[1em] \Rightarrow 81 + 16 + \dfrac{5}{4} \\[1em] \Rightarrow 97 + \dfrac{5}{4} \\[1em] \Rightarrow \dfrac{388 + 5}{4} \\[1em] \Rightarrow \dfrac{393}{4} \\[1em] \Rightarrow 98.25

Hence, (27)43+(32)0.8+(0.8)−1(27)^{\dfrac{4}{3}} + (32)^{0.8} + (0.8)^{-1} = 98.25

Question 17(i)

Simplify the following:

(32−5)13(32+5)13(\sqrt{32} - \sqrt{5})^{\dfrac{1}{3}}(\sqrt{32} + \sqrt{5})^{\dfrac{1}{3}}

Answer

Given,

⇒(32−5)13(32+5)13⇒[(32−5)(32+5)]13\Rightarrow (\sqrt{32} - \sqrt{5})^{\dfrac{1}{3}}(\sqrt{32} + \sqrt{5})^{\dfrac{1}{3}} \\[1em] \Rightarrow [(\sqrt{32} - \sqrt{5})(\sqrt{32} + \sqrt{5})]^{\dfrac{1}{3}}

As (a - b)(a + b) = a2 - b2 we get,

⇒[(32)2−(52)]13⇒[32−5]13⇒(27)13⇒(33)13⇒3.\Rightarrow [(\sqrt{32})^2 - (\sqrt{5}^2)]^{\dfrac{1}{3}} \\[1em] \Rightarrow [32 - 5]^{\dfrac{1}{3}} \\[1em] \Rightarrow (27)^{\dfrac{1}{3}} \\[1em] \Rightarrow (3^3)^{\dfrac{1}{3}} \\[1em] \Rightarrow 3.

Hence, (32−5)13(32+5)13(\sqrt{32} - \sqrt{5})^{\dfrac{1}{3}}(\sqrt{32} + \sqrt{5})^{\dfrac{1}{3}} = 3.

Question 17(ii)

Simplify the following:

(x13−x−13)(x23+1+x−23)\Big(x^{\dfrac{1}{3}} - x^{-\dfrac{1}{3}}\Big)\Big(x^{\dfrac{2}{3}} + 1 + x^{-\dfrac{2}{3}}\Big)

Answer

The above equation can be written as,

⇒(x13−x−13)[(x13)2+x13.x−13+(x−13)2)\Rightarrow \Big(x^{\dfrac{1}{3}} - x^{-\dfrac{1}{3}}\Big)\Big[\Big(x^{\dfrac{1}{3}}\Big)^2 + x^{\dfrac{1}{3}}.x^{-\dfrac{1}{3}} + \Big(x^{-\dfrac{1}{3}}\Big)^2\Big)

We know that,

a3 - b3 = (a - b)(a2 + ab + b2)

∴(x13−x−13)[(x13)2+x13.x−13+(x−13)2]=(x13)3−(x−13)3⇒(x3×13)−(x3×−13)⇒x1−x−1⇒x−1x.\therefore \Big(x^{\dfrac{1}{3}} - x^{-\dfrac{1}{3}}\Big)\Big[\Big(x^{\dfrac{1}{3}}\Big)^2 + x^{\dfrac{1}{3}}.x^{-\dfrac{1}{3}} + \Big(x^{-\dfrac{1}{3}}\Big)^2\Big] = \Big(x^{\dfrac{1}{3}}\Big)^3 - \Big(x^{-\dfrac{1}{3}}\Big)^3 \\[1em] \Rightarrow \Big(x^{3 \times \dfrac{1}{3}}\Big) - \Big(x^{3 \times -\dfrac{1}{3}}\Big) \\[1em] \Rightarrow x^1 - x^{-1} \\[1em] \Rightarrow x - \dfrac{1}{x}.

Hence, (x13−x−13)(x23+1+x−23)=x−1x\Big(x^{\dfrac{1}{3}} - x^{-\dfrac{1}{3}}\Big)\Big(x^{\dfrac{2}{3}} + 1 + x^{-\dfrac{2}{3}}\Big) = x - \dfrac{1}{x}.

Question 18(i)

Simplify the following:

(xmxn)l.(xnxl)m.(xlxm)n\Big(\dfrac{x^m}{x^n}\Big)^l.\Big(\dfrac{x^n}{x^l}\Big)^m.\Big(\dfrac{x^l}{x^m}\Big)^n

Answer

Given,

⇒(xmxn)l.(xnxl)m.(xlxm)n=(xm.x−n)l.(xn.x−l)m.(xl.x−m)n=(xm−n)l.(xn−l)m.(xl−m)n=xml−nl.xnm−lm.xln−mn=xml−nl+nm−lm+ln−mn=x0=1.\Rightarrow \Big(\dfrac{x^m}{x^n}\Big)^l.\Big(\dfrac{x^n}{x^l}\Big)^m.\Big(\dfrac{x^l}{x^m}\Big)^n = (x^m.x^{-n})^l.(x^n.x^{-l})^m.(x^l.x^{-m})^n \\[1em] = (x^{m - n})^l.(x^{n - l})^m.(x^{l - m})^n \\[1em] = x^{ml - nl}.x^{nm - lm}.x^{ln - mn} \\[1em] = x^{ml - nl + nm - lm + ln - mn} \\[1em] = x^0 = 1.

Hence, (xmxn)l.(xnxl)m.(xlxm)n\Big(\dfrac{x^m}{x^n}\Big)^l.\Big(\dfrac{x^n}{x^l}\Big)^m.\Big(\dfrac{x^l}{x^m}\Big)^n = 1.

Question 18(ii)

Simplify the following:

(xa+bxc)a−b.(xb+cxa)b−c.(xc+axb)c−a\Big(\dfrac{x^{a + b}}{x^c}\Big)^{a - b}.\Big(\dfrac{x^{b + c}}{x^a}\Big)^{b - c}.\Big(\dfrac{x^{c + a}}{x^b}\Big)^{c - a}

Answer

Given,

⇒(xa+bxc)a−b.(xb+cxa)b−c.(xc+axb)c−a=(xa+b−c)a−b.(xb+c−a)b−c.(xc+a−b)c−a=x(a2−ab+ba−b2−ca+cb).x(b2−bc+cb−c2−ab+ac).xc2−ca+ac−a2−bc+ba=xa2−ab+ba−b2−ca+cb+b2−bc+cb−c2−ab+ac+c2−ca+ac−a2−bc+ba=xa2−a2−ab+ba−b2+b2−ca+ac+cb−bc+cb−bc−ab+ba−ca+ac−c2+c2=x0=1.\Rightarrow \Big(\dfrac{x^{a + b}}{x^c}\Big)^{a - b}.\Big(\dfrac{x^{b + c}}{x^a}\Big)^{b - c}.\Big(\dfrac{x^{c + a}}{x^b}\Big)^{c - a} \\[1em] = (x^{a + b - c})^{a - b}.(x^{b + c - a})^{b - c}.(x^{c + a - b})^{c - a} \\[1em] = x^{(a^2 - ab + ba - b^2 - ca + cb)}.x^{(b^2 - bc + cb - c^2 - ab + ac)}.x^{c^2 - ca + ac - a^2 - bc + ba} \\[1em] = x^{a^2 - ab + ba - b^2 - ca + cb + b^2 - bc + cb - c^2 - ab + ac + c^2 - ca + ac - a^2 - bc + ba} \\[1em] = x^{a^2 - a^2 - ab + ba - b^2 + b^2 - ca + ac + cb - bc + cb - bc - ab + ba - ca + ac - c^2 + c^2} \\[1em] = x^0 = 1.

Hence, (xa+bxc)a−b.(xb+cxa)b−c.(xc+axb)c−a\Big(\dfrac{x^{a + b}}{x^c}\Big)^{a - b}.\Big(\dfrac{x^{b + c}}{x^a}\Big)^{b - c}.\Big(\dfrac{x^{c + a}}{x^b}\Big)^{c - a} = 1.

Question 19(i)

Simplify the following:

xlxmlm.xmxnmn.xnxlnl\sqrt[lm]{\dfrac{x^l}{x^m}}.\sqrt[mn]{\dfrac{x^m}{x^n}}.\sqrt[nl]{\dfrac{x^n}{x^l}}

Answer

Given,

⇒xlxmlm.xmxnmn.xnxlnl=xl−mlm.xm−nmn.xn−lnl=(x)l−mlm.(x)m−nmn.(x)n−lnl=(x)l−mlm+m−nmn+n−lnl=(x)(l−m)n+(m−n)l+(n−l)mlmn=(x)ln−mn+ml−nl+nm−lmlmn=(x)0=1.\Rightarrow \sqrt[lm]{\dfrac{x^l}{x^m}}.\sqrt[mn]{\dfrac{x^m}{x^n}}.\sqrt[nl]{\dfrac{x^n}{x^l}} \\[1em] = \sqrt[lm]{x^{l - m}}.\sqrt[mn]{x^{m - n}}.\sqrt[nl]{x^{n - l}} \\[1em] = (x)^{\dfrac{l - m}{lm}}.(x )^{\dfrac{m - n}{mn}}.(x)^{\dfrac{n - l}{nl}} \\[1em] = (x)^{\dfrac{l - m}{lm} + \dfrac{m - n}{mn} + \dfrac{n - l}{nl}} \\[1em] = (x)^{\dfrac{(l - m)n + (m - n)l + (n - l)m}{lmn}} \\[1em] = (x)^{\dfrac{ln - mn + ml - nl + nm - lm}{lmn}} \\[1em] = (x)^0 \\[1em] = 1.

Hence, xlxmlm.xmxnmn.xnxlnl\sqrt[lm]{\dfrac{x^l}{x^m}}.\sqrt[mn]{\dfrac{x^m}{x^n}}.\sqrt[nl]{\dfrac{x^n}{x^l}} = 1.

Question 19(ii)

Simplify the following:

(xaxb)a2+ab+b2.(xbxc)b2+bc+c2.(xcxa)c2+ac+a2\Big(\dfrac{x^a}{x^b}\Big)^{a^2 + ab + b^2}.\Big(\dfrac{x^b}{x^c}\Big)^{b^2 + bc + c^2}.\Big(\dfrac{x^c}{x^a}\Big)^{c^2 + ac + a^2}

Answer

Given,

⇒(xaxb)a2+ab+b2.(xbxc)b2+bc+c2.(xcxa)c2+ac+a2⇒(x(a−b))(a2+ab+b2).(x(b−c))(b2+bc+c2).(x(c−a))(c2+ca+a2)\Rightarrow \Big(\dfrac{x^a}{x^b}\Big)^{a^2 + ab + b^2}.\Big(\dfrac{x^b}{x^c}\Big)^{b^2 + bc + c^2}.\Big(\dfrac{x^c}{x^a}\Big)^{c^2 + ac + a^2} \\[1em] \Rightarrow (x^{(a - b)})^{(a^2 + ab + b^2)}.(x^{(b - c)})^{(b^2 + bc + c^2)}.(x^{(c - a)})^{(c^2 + ca + a^2)}

By formula,

(x3 - y3) = (x - y)(x2 + y2 + xy) we get,

⇒(x)a3−b3.(x)b3−c3.(x)c3−a3⇒xa3−b3+b3−c3+c3−a3⇒x0=1.\Rightarrow (x)^{a^3 - b^3}.(x)^{b^3 - c^3}.(x)^{c^3 - a^3} \\[1em] \Rightarrow x^{a^3 - b^3 + b^3 - c^3 + c^3 - a^3} \\[1em] \Rightarrow x^{0} = 1.

Hence, (xaxb)a2+ab+b2.(xbxc)b2+bc+c2.(xcxa)c2+ac+a2\Big(\dfrac{x^a}{x^b}\Big)^{a^2 + ab + b^2}.\Big(\dfrac{x^b}{x^c}\Big)^{b^2 + bc + c^2}.\Big(\dfrac{x^c}{x^a}\Big)^{c^2 + ac + a^2} = 1.

Question 19(iii)

Simplify the following:

(xax−b)a2−ab+b2.(xbx−c)b2−bc+c2.(xcx−a)c2−ca+a2\Big(\dfrac{x^a}{x^{-b}}\Big)^{a^2 - ab + b^2}.\Big(\dfrac{x^b}{x^{-c}}\Big)^{b^2 - bc + c^2}.\Big(\dfrac{x^c}{x^{-a}}\Big)^{c^2 - ca + a^2}

Answer

Given,

⇒(xax−b)a2−ab+b2.(xbx−c)b2−bc+c2.(xcx−a)c2−ca+a2⇒(x(a−(−b)))(a2−ab+b2).(x(b−(−c)))(b2−bc+c2).(x(c−(−a)))(c2−ca+a2)⇒(x(a+b))(a2−ab+b2).(x(b+c))(b2−bc+c2).(x(c+a))(c2−ca+a2)\Rightarrow \Big(\dfrac{x^a}{x^{-b}}\Big)^{a^2 - ab + b^2}.\Big(\dfrac{x^b}{x^{-c}}\Big)^{b^2 - bc + c^2}.\Big(\dfrac{x^c}{x^{-a}}\Big)^{c^2 - ca + a^2} \\[1em] \Rightarrow (x^{(a - (-b))})^{(a^2 - ab + b^2)}.(x^{(b - (-c))})^{(b^2 - bc + c^2)}.(x^{(c - (-a))})^{(c^2 - ca + a^2)} \\[1em] \Rightarrow (x^{(a + b)})^{(a^2 - ab + b^2)}.(x^{(b + c)})^{(b^2 - bc + c^2)}.(x^{(c + a)})^{(c^2 - ca + a^2)}

By formula,

(x3 + y3) = (x + y)(x2 + y2 - xy) we get,

⇒(x)a3+b3.(x)b3+c3.(x)c3+a3⇒xa3+b3+b3+c3+c3+a3⇒x2(a3+b3+c3).\Rightarrow (x)^{a^3 + b^3}.(x)^{b^3 + c^3}.(x)^{c^3 + a^3} \\[1em] \Rightarrow x^{a^3 + b^3 + b^3 + c^3 + c^3 + a^3} \\[1em] \Rightarrow x^{2(a^3 + b^3 + c^3)}.

Hence, (xax−b)a2−ab+b2.(xbx−c)b2−bc+c2.(xcx−a)c2−ca+a2=x2(a3+b3+c3)\Big(\dfrac{x^a}{x^{-b}}\Big)^{a^2 - ab + b^2}.\Big(\dfrac{x^b}{x^{-c}}\Big)^{b^2 - bc + c^2}.\Big(\dfrac{x^c}{x^{-a}}\Big)^{c^2 - ca + a^2} = x^{2(a^3 + b^3+ c^3)}.

Question 20(i)

Simplify the following:

(a-1 + b-1) ÷ (a-2 - b-2)

Answer

Given,

⇒(a−1+b−1)÷(a−2−b−2)⇒(1a+1b)÷(1a2−1b2)⇒(b+aab)÷(b2−a2a2b2)⇒(b+aab)×(a2b2b2−a2)⇒ab(b+a)b2−a2⇒ab(b+a)(b−a)(b+a)⇒abb−a.\Rightarrow (a^{-1} + b^{-1}) ÷ (a^{-2} - b^{-2}) \\[1em] \Rightarrow \Big(\dfrac{1}{a} + \dfrac{1}{b}\Big) ÷ \Big(\dfrac{1}{a^2} - \dfrac{1}{b^2}\Big) \\[1em] \Rightarrow \Big(\dfrac{b + a}{ab}\Big) ÷ \Big(\dfrac{b^2 - a^2}{a^2b^2}\Big) \\[1em] \Rightarrow \Big(\dfrac{b + a}{ab}\Big) \times \Big(\dfrac{a^2b^2}{b^2 - a^2}\Big) \\[1em] \Rightarrow \dfrac{ab(b + a)}{b^2 - a^2} \\[1em] \Rightarrow \dfrac{ab(b + a)}{(b - a)(b + a)} \\[1em] \Rightarrow \dfrac{ab}{b - a}.

Hence, (a-1 + b-1) ÷ (a-2 - b-2) = abb−a.\dfrac{ab}{b - a}.

Question 20(ii)

Simplify the following:

11+am−n+11+an−m\dfrac{1}{1 + a^{m - n}} + \dfrac{1}{1 + a^{n - m}}

Answer

Given,

⇒11+am−n+11+an−m⇒11+am.a−n+11+an.a−m⇒11+aman+11+anam⇒1an+aman+1am+anam⇒anan+am+amam+an⇒an+aman+am⇒1.\Rightarrow \dfrac{1}{1 + a^{m - n}} + \dfrac{1}{1 + a^{n - m}} \\[1em] \Rightarrow \dfrac{1}{1 + a^m.a^{-n}} + \dfrac{1}{1 + a^n.a^{-m}} \\[1em] \Rightarrow \dfrac{1}{1 + \dfrac{a^m}{a^n}} + \dfrac{1}{1 + \dfrac{a^n}{a^m}} \\[1em] \Rightarrow \dfrac{1}{\dfrac{a^n + a^m}{a^n}} + \dfrac{1}{\dfrac{a^m + a^n}{a^m}} \\[1em] \Rightarrow \dfrac{a^n}{a^n + a^m} + \dfrac{a^m}{a^m + a^n} \\[1em] \Rightarrow \dfrac{a^n + a^m}{a^n + a^m} \\[1em] \Rightarrow 1.

Hence, 11+am−n+11+an−m\dfrac{1}{1 + a^{m - n}} + \dfrac{1}{1 + a^{n - m}} = 1.

Question 21(i)

Prove the following:

(a + b)-1(a-1 + b-1) = 1ab\dfrac{1}{ab}

Answer

Given,

⇒(a+b)−1(a−1+b−1)=1ab\Rightarrow (a + b)^{-1}(a^{-1} + b^{-1}) = \dfrac{1}{ab}

Solving L.H.S. of above equation,

⇒1a+b×(1a+1b)⇒1a+b×(b+aab)⇒1ab.\Rightarrow \dfrac{1}{a + b} \times \Big(\dfrac{1}{a} + \dfrac{1}{b}\Big) \\[1em] \Rightarrow \dfrac{1}{a + b} \times \Big(\dfrac{b + a}{ab}\Big) \\[1em] \Rightarrow \dfrac{1}{ab}.

Since, L.H.S. = R.H.S.

Hence, proved that (a + b)-1(a-1 + b-1) = 1ab\dfrac{1}{ab}.

Question 21(ii)

Prove the following:

x+y+zx−1y−1+y−1z−1+z−1x−1=xyz\dfrac{x + y + z}{x^{-1}y^{-1} + y^{-1}z^{-1} + z^{-1}x^{-1}} = xyz

Answer

Given,

x+y+zx−1y−1+y−1z−1+z−1x−1=xyz\dfrac{x + y + z}{x^{-1}y^{-1} + y^{-1}z^{-1} + z^{-1}x^{-1}} = xyz

Solving L.H.S. of above equation,

⇒x+y+z1xy+1yz+1zx⇒x+y+zz+x+yxyz⇒xyz(x+y+z)x+y+z⇒xyz.\Rightarrow \dfrac{x + y + z}{\dfrac{1}{xy} + \dfrac{1}{yz} + \dfrac{1}{zx}} \\[1em] \Rightarrow \dfrac{x + y + z}{\dfrac{z + x + y}{xyz}} \\[1em] \Rightarrow \dfrac{xyz(x + y + z)}{x + y + z} \\[1em] \Rightarrow xyz.

Hence, proved that x+y+zx−1y−1+y−1z−1+z−1x−1\dfrac{x + y + z}{x^{-1}y^{-1} + y^{-1}z^{-1} + z^{-1}x^{-1}} = xyz.

Question 22

If a = cz, b = ax and c = by, prove that xyz = 1.

Answer

Given,

a = cz, b = ax and c = by

Substituting value of c in a = cz we get,

⇒ a = (by)z = byz

Substituting value of b in above equation we get,

⇒ a = (ax)yz
⇒ a = axyz

∴ xyz = 1.

Hence, proved that xyz = 1.

Question 23

If a = xyp - 1, b = xyq - 1 and c = xyr - 1, prove that

aq - r.br - p.cp - q = 1.

Answer

Given,

a = xyp - 1, b = xyq - 1 and c = xyr - 1.

Substituting value of a, b and c in L.H.S. of aq - r.br - p.cp - q = 1 we get,

⇒ (xyp - 1)q - r.(xyq - 1)r - p.(xyr - 1)p - q

⇒ (xy)(p - 1)(q - r).(xy)(q - 1)(r - p).(xy)(r - 1)(p - q)

⇒ (xy)(p - 1)(q - r) + (q - 1)(r - p) + (r - 1)(p - q)

⇒ (xy)pq - pr - q + r + qr - qp - r + p + rp - rq - p + q

⇒ (xy)p - p - q + q + r - r + pq - qp - pr + rp + qr - rq

⇒ (xy)0

⇒ 1.

Hence,prove that aq - r.br - p.cp - q = 1.

Question 24

If 2x = 3y = 6-z, prove that 1x+1y+1z=0.\dfrac{1}{x} + \dfrac{1}{y} + \dfrac{1}{z} = 0.

Answer

Let 2x = 3y = 6-z = k.

∴2x=k or 2=k1x\therefore 2^x = k \text{ or } 2 = k^{\dfrac{1}{x}} ......(i)

∴3y=k or 3=k1y\therefore 3^y = k \text{ or } 3 = k^{\dfrac{1}{y}} ......(ii)

∴6−z=k or 6=k−1z\therefore 6^{-z} = k \text{ or } 6 = k^{-\dfrac{1}{z}} ......(iii)

We know that,

2 × 3 = 6

Substituting value of 2, 3 and 6 from (i), (ii) and (iii) in above equation we get,

⇒k1x×k1y=k−1z⇒k1x+1y=k−1z∴1x+1y=−1z⇒1x+1y+1z=0.\Rightarrow k^{\dfrac{1}{x}} \times k^{\dfrac{1}{y}} = k^{-\dfrac{1}{z}} \\[1em] \Rightarrow k^{\dfrac{1}{x} + \dfrac{1}{y}} = k^{-\dfrac{1}{z}} \\[1em] \therefore \dfrac{1}{x} + \dfrac{1}{y} = -\dfrac{1}{z} \\[1em] \Rightarrow \dfrac{1}{x} + \dfrac{1}{y} + \dfrac{1}{z} = 0.

Hence, proved that 1x+1y+1z=0\dfrac{1}{x} + \dfrac{1}{y} + \dfrac{1}{z} = 0.

Question 25

If 2x = 3y = 12z, prove that x = 2yzy−z.\dfrac{2yz}{y - z}.

Answer

Let 2x = 3y = 12z = k.

∴2x=k or 2=k1x\therefore 2^x = k \text{ or } 2 = k^{\dfrac{1}{x}} ......(i)

∴3y=k or 3=k1y\therefore 3^y = k \text{ or } 3 = k^{\dfrac{1}{y}} ......(ii)

∴12z=k or 12=k1z\therefore 12^{z} = k \text{ or } 12 = k^{\dfrac{1}{z}} ......(iii)

We know that,

22 × 3 = 12

Substituting value of 2, 3 and 12 from (i), (ii) and (iii) in above equation we get,

⇒(k1x)2×k1y=k1z⇒k2x×k1y=k1z⇒k2x+1y=k1z∴2x+1y=1z⇒2x=1z−1y⇒2x=y−zyz⇒x2=yzy−z⇒x=2yzy−z.\Rightarrow (k^{\dfrac{1}{x}})^2 \times k^{\dfrac{1}{y}} = k^{\dfrac{1}{z}} \\[1em] \Rightarrow k^{\dfrac{2}{x}} \times k^{\dfrac{1}{y}} = k^{\dfrac{1}{z}} \\[1em] \Rightarrow k^{\dfrac{2}{x} + \dfrac{1}{y}} = k^{\dfrac{1}{z}} \\[1em] \therefore \dfrac{2}{x} + \dfrac{1}{y} = \dfrac{1}{z} \\[1em] \Rightarrow \dfrac{2}{x} = \dfrac{1}{z} - \dfrac{1}{y} \\[1em] \Rightarrow \dfrac{2}{x} = \dfrac{y - z}{yz} \\[1em] \Rightarrow \dfrac{x}{2} = \dfrac{yz}{y - z} \\[1em] \Rightarrow x = \dfrac{2yz}{y - z}.

Hence, proved that x=2yzy−z.x = \dfrac{2yz}{y - z}.

Question 26

Simplify and express with positive exponents:

(3x2)0,(xy)−2,(−27a9)23(3x^2)^0, (xy)^{-2}, (-27a^9)^{\dfrac{2}{3}}

Answer

(3x2)0 = 1,

(xy)−2=(1xy)2=1x2y2(xy)^{-2} = \Big(\dfrac{1}{xy}\Big)^2 = \dfrac{1}{x^2y^2}

(−27a9)23=[(−3a3)3]23=(−3a3)3×23=(−3a3)2=9a6.(-27a^9)^{\dfrac{2}{3}} = [(-3a^3)^3]^{\dfrac{2}{3}} \\[1em] = (-3a^3)^{3 \times \dfrac{2}{3}} \\[1em] = (-3a^3)^2 \\[1em] = 9a^6.

Question 27

If a = 3 and b = -2, find the values of:

(i) aa + bb

(ii) ab + ba

Answer

(i) Given, a = 3 and b = -2.

Substituting values of a and b in aa + bb we get,

= 33 + (-2)-2

= 27 + (−12)2\Big(-\dfrac{1}{2}\Big)^2

= 27 + 14=2714\dfrac{1}{4} = 27\dfrac{1}{4}.

Hence, aa+bb=2714.a^a + b^b = 27\dfrac{1}{4}.

(ii) Given, a = 3 and b = -2.

Substituting values of a and b in ab + ba we get,

=(3)−2+(−2)3=(13)2+(−8)=19−8=1−729=−719=−789.= (3)^{-2} + (-2)^3 \\[1em] = \Big(\dfrac{1}{3}\Big)^2 + (-8) \\[1em] = \dfrac{1}{9} - 8 \\[1em] = \dfrac{1 - 72}{9} \\[1em] = -\dfrac{71}{9} = -7\dfrac{8}{9}.

Hence, aa+bb=−789.a^a + b^b = -7\dfrac{8}{9}.

Question 28

If x = 103 × 0.0099, y = 10-2 × 110, find the value of xy\sqrt{\dfrac{x}{y}}.

Answer

Substituting value of x and y in xy\sqrt{\dfrac{x}{y}} we get,

⇒xy=103×0.009910−2×110=9.910−2×110=9.9×102110=990110=9=3.\Rightarrow \sqrt{\dfrac{x}{y}} = \sqrt{\dfrac{10^3 \times 0.0099}{10^{-2} \times 110}} \\[1em] = \sqrt{\dfrac{9.9}{10^{-2} \times 110}} \\[1em] = \sqrt{\dfrac{9.9 \times 10^2}{110}} \\[1em] = \sqrt{\dfrac{990}{110}} \\[1em] = \sqrt{9} = 3.

Hence, xy=3.\sqrt{\dfrac{x}{y}} = 3.

Question 29

Evaluate x12.y−1.z23x^{\dfrac{1}{2}}.y^{-1}.z^{\dfrac{2}{3}} when x = 9, y = 2 and z = 8.

Answer

Substituting value of x, y and z in x12.y−1.z23x^{\dfrac{1}{2}}.y^{-1}.z^{\dfrac{2}{3}} we get,

⇒x12.y−1.z23=(9)12.(2)−1.(8)23=(32)12×12×(23)23=3×12×22=122=6.\Rightarrow x^{\dfrac{1}{2}}.y^{-1}.z^{\dfrac{2}{3}} = (9)^{\dfrac{1}{2}}.(2)^{-1}.(8)^{\dfrac{2}{3}} \\[1em] = (3^2)^{\dfrac{1}{2}} \times \dfrac{1}{2} \times (2^3)^{\dfrac{2}{3}} \\[1em] = 3 \times \dfrac{1}{2} \times 2^2 \\[1em] = \dfrac{12}{2} = 6.

Hence, x12.y−1.z23x^{\dfrac{1}{2}}.y^{-1}.z^{\dfrac{2}{3}} = 6.

Question 30

If x4y2z3 = 49392, find the values of x, y and z, where x, y and z are different positive primes.

Answer

On prime factorization of 49392 we get,

49392 = 243273

∴ x4y2z3 = 243273

On comparing we get,

x = 2, y = 3 and z = 7.

Hence, x = 2, y = 3 and z = 7.

Question 31

If a6b−43=ax.b2y\sqrt[3]{a^6b^{-4}} = a^x.b^{2y}, find x and y, where a, b are different positive primes.

Answer

Given,

⇒a6b−43=ax.b2y⇒(a6b−4)13=ax.b2y⇒a63.b−43=ax.b2y⇒a2.b−43=ax.b2y∴x=2 and 2y=−43⇒x=2 and y=−23.\Rightarrow \sqrt[3]{a^6b^{-4}} = a^x.b^{2y} \\[1em] \Rightarrow (a^6b^{-4})^{\dfrac{1}{3}} = a^x.b^{2y} \\[1em] \Rightarrow a^{\dfrac{6}{3}}.b^{-\dfrac{4}{3}} = a^x.b^{2y} \\[1em] \Rightarrow a^2.b^{-\dfrac{4}{3}} = a^x.b^{2y} \\[1em] \therefore x = 2 \text{ and } 2y = -\dfrac{4}{3} \\[1em] \Rightarrow x = 2 \text{ and } y = -\dfrac{2}{3}.

Hence, x = 2 and y = −23-\dfrac{2}{3}.

Question 32

If (p + q)-1(p-1 + q-1) = paqb, prove that a + b +2 = 0, where p and q are different positive primes.

Answer

Given,

⇒(p+q)−1(p−1+q−1)=paqb⇒1(p+q)(1p+1q)=paqb⇒1(p+q)×p+qpq=paqb⇒1pq=paqb⇒p−1q−1=paqb∴a=−1 and b=−1.\Rightarrow (p + q)^{-1}(p^{-1} + q^{-1}) = p^aq^b \\[1em] \Rightarrow \dfrac{1}{(p + q)}\Big(\dfrac{1}{p} + \dfrac{1}{q}\Big) = p^aq^b \\[1em] \Rightarrow \dfrac{1}{(p + q)} \times \dfrac{p + q}{pq} = p^aq^b \\[1em] \Rightarrow \dfrac{1}{pq} = p^aq^b \\[1em] \Rightarrow p^{-1}q^{-1} = p^aq^b \\[1em] \therefore a = -1 \text{ and } b = -1.

Substituting values of a and b in L.H.S. of a + b + 2 = 0 we get,

a + b + 2 = -1 + (-1) + 2 = -2 + 2 = 0.

Hence, proved that a + b + 2 = 0.

Question 33

If (p−1q2p2q−4)7÷(p3q−5p−2q3)−5=pxqy\Big(\dfrac{p^{-1}q^{2}}{p^2q^{-4}}\Big)^7 ÷ \Big(\dfrac{p^3q^{-5}}{p^{-2}q^{3}}\Big)^{-5} = p^xq^y, find x + y, where p and q are different positive primes.

Answer

Given,

⇒(p−1q2p2q−4)7÷(p3q−5p−2q3)−5=pxqy⇒(p−1q2p2q−4)7÷(p−2q3p3q−5)5=pxqy⇒p−7q14p14q−28×(p3q−5p−2q3)5=pxqy⇒q14.q28p14.p7×p15q−25p−10q15=pxqy⇒q14+28p14+7×p15.p10q25.q15=pxqy⇒q42p21×p25q40=pxqy⇒p4q2=pxqy∴x=4 and y=2.\Rightarrow \Big(\dfrac{p^{-1}q^{2}}{p^2q^{-4}}\Big)^7 ÷ \Big(\dfrac{p^3q^{-5}}{p^{-2}q^{3}}\Big)^{-5} = p^xq^y \\[1em] \Rightarrow \Big(\dfrac{p^{-1}q^{2}}{p^2q^{-4}}\Big)^7 ÷ \Big(\dfrac{p^{-2}q^3}{p^3q^{-5}}\Big)^5 = p^xq^y \\[1em] \Rightarrow \dfrac{p^{-7}q^{14}}{p^{14}q^{-28}} \times \Big(\dfrac{p^3q^{-5}}{p^{-2}q^3}\Big)^5 = p^xq^y \\[1em] \Rightarrow \dfrac{q^{14}.q^{28}}{p^{14}.p^7} \times \dfrac{p^{15}q^{-25}}{p^{-10}q^{15}} = p^xq^y \\[1em] \Rightarrow \dfrac{q^{14 +28}}{p^{14 + 7}} \times \dfrac{p^{15}.p^{10}}{q^{25}.q^{15}} = p^xq^y \\[1em] \Rightarrow \dfrac{q^{42}}{p^{21}} \times \dfrac{p^{25}}{q^{40}} = p^xq^y \\[1em] \Rightarrow p^{4}q^{2} = p^xq^y \\[1em] \therefore x = 4 \text{ and } y = 2.

x + y = 4 + 2 = 6.

Hence, x + y = 6.

Question 34(i)

Solve the following equation for x:

52x + 3 = 1

Answer

Given,

⇒ 52x + 3 = 1

⇒ 52x + 3 = 50

⇒ 2x + 3 = 0

⇒ 2x = -3

⇒ x = -32\dfrac{3}{2}.

Hence, x = -32\dfrac{3}{2}.

Question 34(ii)

Solve the following equation for x:

(13)x=44−34−6(13)^{\sqrt{x}} = 4^4 - 3^4 - 6

Answer

Given,

⇒(13)x=44−34−6⇒(13)x=256−81−6⇒(13)x=169⇒(13)x=132∴x=2⇒x=4.\Rightarrow (13)^{\sqrt{x}} = 4^4 - 3^4 - 6 \\[1em] \Rightarrow (13)^{\sqrt{x}} = 256 - 81 - 6 \\[1em] \Rightarrow (13)^{\sqrt{x}} = 169 \\[1em] \Rightarrow (13)^{\sqrt{x}} = 13^2 \\[1em] \therefore \sqrt{x} = 2 \\[1em] \Rightarrow x = 4.

Hence, x = 4.

Question 34(iii)

Solve the following equation for x:

(35)x+1=12527\Big(\sqrt{\dfrac{3}{5}}\Big)^{x + 1} = \dfrac{125}{27}

Answer

Given,

⇒(35)x+1=12527⇒(35)x+12=(53)3⇒(35)x+12=(35)−3∴x+12=−3⇒x+1=−6⇒x=−7.\Rightarrow \Big(\sqrt{\dfrac{3}{5}}\Big)^{x + 1} = \dfrac{125}{27} \\[1em] \Rightarrow \Big(\dfrac{3}{5}\Big)^{\dfrac{x + 1}{2}} = \Big(\dfrac{5}{3}\Big)^3 \\[1em] \Rightarrow \Big(\dfrac{3}{5}\Big)^{\dfrac{x + 1}{2}} = \Big(\dfrac{3}{5}\Big)^{-3} \\[1em] \therefore \dfrac{x + 1}{2} = -3 \\[1em] \Rightarrow x + 1 = -6 \\[1em] \Rightarrow x = -7.

Hence, x = -7.

Question 34(iv)

Solve the following equation for x:

(43)2x+12=132(\sqrt[3]{4})^{2x + \dfrac{1}{2}} = \dfrac{1}{32}

Answer

Given,

⇒(43)2x+12=132⇒[(22)13]2x+12=125⇒(22)2x3+16=2−5⇒(2)4x3+13=2−5⇒4x+13=−5⇒4x+1=−15⇒4x=−16⇒x=−4.\Rightarrow (\sqrt[3]{4})^{2x + \dfrac{1}{2}} = \dfrac{1}{32} \\[1em] \Rightarrow [(2^2)^{\dfrac{1}{3}}]^{2x + \dfrac{1}{2}} = \dfrac{1}{2^5} \\[1em] \Rightarrow (2^2)^{\dfrac{2x}{3} + \dfrac{1}{6}} = 2^{-5} \\[1em] \Rightarrow (2)^{\dfrac{4x}{3} + \dfrac{1}{3}} = 2^{-5} \\[1em] \Rightarrow \dfrac{4x + 1}{3} = -5 \\[1em] \Rightarrow 4x + 1 = -15 \\[1em] \Rightarrow 4x = -16 \\[1em] \Rightarrow x = -4.

Hence, x = -4.

Question 35(i)

Solve the following equation for x:

pq=(qp)1−2x\sqrt{\dfrac{p}{q}} = \Big(\dfrac{q}{p}\Big)^{1 - 2x}

Answer

Given,

⇒pq=(qp)1−2x⇒(pq)12=(pq)−(1−2x)⇒(pq)12=(pq)(2x−1)⇒12=2x−1⇒2x=1+12⇒2x=32⇒x=34.\Rightarrow \sqrt{\dfrac{p}{q}} = \Big(\dfrac{q}{p}\Big)^{1 - 2x} \\[1em] \Rightarrow \Big(\dfrac{p}{q}\Big)^{\dfrac{1}{2}} = \Big(\dfrac{p}{q}\Big)^{-(1 - 2x)} \\[1em] \Rightarrow \Big(\dfrac{p}{q}\Big)^{\dfrac{1}{2}} = \Big(\dfrac{p}{q}\Big)^{(2x - 1)} \\[1em] \Rightarrow \dfrac{1}{2} = 2x - 1 \\[1em] \Rightarrow 2x = 1 + \dfrac{1}{2} \\[1em] \Rightarrow 2x = \dfrac{3}{2} \\[1em] \Rightarrow x = \dfrac{3}{4}.

Hence, x = 34\dfrac{3}{4}.

Question 35(ii)

Solve the following equation for x:

4x−1×(0.5)3−2x=(18)x4^{x - 1} \times (0.5)^{3 - 2x} = \Big(\dfrac{1}{8}\Big)^x

Answer

Given,

⇒4x−1×(0.5)3−2x=(18)x⇒(22)x−1×(510)3−2x=(123)x⇒22x−2×(12)3−2x=(2−3)x⇒22x−2×(2−1)3−2x=2−3x⇒22x−2×22x−3=2−3x⇒22x−2+2x−3=2−3x⇒24x−5=2−3x⇒4x−5=−3x⇒4x+3x=5⇒7x=5⇒x=57.\Rightarrow 4^{x - 1} \times (0.5)^{3 - 2x} = \Big(\dfrac{1}{8}\Big)^x \\[1em] \Rightarrow (2^2)^{x - 1} \times \Big(\dfrac{5}{10}\Big)^{3 - 2x} = \Big(\dfrac{1}{2^3}\Big)^x \\[1em] \Rightarrow 2^{2x - 2} \times \Big(\dfrac{1}{2}\Big)^{3 - 2x} = (2^{-3})^x \\[1em] \Rightarrow 2^{2x - 2} \times (2^{-1})^{3 - 2x} = 2^{-3x} \\[1em] \Rightarrow 2^{2x - 2} \times 2^{2x - 3} = 2^{-3x} \\[1em] \Rightarrow 2^{2x - 2 + 2x - 3} = 2^{-3x} \\[1em] \Rightarrow 2^{4x - 5} = 2^{-3x} \\[1em] \Rightarrow 4x - 5 = -3x \\[1em] \Rightarrow 4x + 3x = 5 \\[1em] \Rightarrow 7x = 5 \\[1em] \Rightarrow x = \dfrac{5}{7}.

Hence, x = 57\dfrac{5}{7}.

Question 36

If 53x = 125 and (10)y = 0.001, find x and y.

Answer

Given,

⇒ 53x = 125

⇒ 53x = 53

⇒ 3x = 3

⇒ x = 1.

Given,

⇒10y=0.001⇒10y=11000⇒10y=1103⇒10y=10−3⇒y=−3.\Rightarrow 10^y = 0.001 \\[1em] \Rightarrow 10^y = \dfrac{1}{1000} \\[1em] \Rightarrow 10^y = \dfrac{1}{10^3} \\[1em] \Rightarrow 10^y = 10^{-3} \\[1em] \Rightarrow y = -3.

Hence, x = 1 and y = -3.

Question 37

If 9n.32.3n−(27)n33m.23=127\dfrac{9^n.3^2.3^n - (27)^n}{3^{3m}.2^3} = \dfrac{1}{27}, prove that m = 1 + n.

Answer

Given,

⇒9n.32.3n−(27)n33m.23=127⇒(32)n.32.3n−(33)n33m.8=133⇒32n+n.32−33n33m.8=133⇒33n.9−33n33m.8=133⇒33n(9−1)33m.8=133⇒33n.833m.8=3−3⇒33n33m=3−3⇒33n=33m.3−3⇒33n=33m+(−3)⇒3n=3m−3⇒3n=3(m−1)⇒n=m−1⇒m=1+n.\Rightarrow \dfrac{9^n.3^2.3^n - (27)^n}{3^{3m}.2^3} = \dfrac{1}{27} \\[1em] \Rightarrow \dfrac{(3^2)^n.3^2.3^n - (3^3)^n}{3^{3m}.8} = \dfrac{1}{3^3} \\[1em] \Rightarrow \dfrac{3^{2n + n}.3^2 - 3^{3n}}{3^{3m}.8} = \dfrac{1}{3^3} \\[1em] \Rightarrow \dfrac{3^{3n}.9 - 3^{3n}}{3^{3m}.8} = \dfrac{1}{3^3} \\[1em] \Rightarrow \dfrac{3^{3n}(9 - 1)}{3^{3m}.8} = \dfrac{1}{3^3} \\[1em] \Rightarrow \dfrac{3^{3n}.8}{3^{3m}.8} = 3^{-3} \\[1em] \Rightarrow \dfrac{3^{3n}}{3^{3m}} = 3^{-3} \\[1em] \Rightarrow 3^{3n} = 3^{3m}.3^{-3} \\[1em] \Rightarrow 3^{3n} = 3^{3m + (-3)} \\[1em] \Rightarrow 3n = 3m - 3 \\[1em] \Rightarrow 3n = 3(m - 1) \\[1em] \Rightarrow n = m - 1 \\[1em] \Rightarrow m = 1 + n.

Hence, proved that m = 1 + n.

Question 38

If 34x = 81-1 and (10)1y(10)^{\dfrac{1}{y}} = 0.0001, find the value of 2-x.(16)y.

Answer

Given,

⇒ 34x = 81-1

⇒ 34x = (34)-1

⇒ 34x = (3-4)

⇒ 4x = -4

⇒ x = -1.

Given,

⇒(10)1y=0.0001⇒(10)1y=1104⇒(10)1y=10−4⇒1y=−4⇒y=−14.\Rightarrow (10)^{\dfrac{1}{y}} = 0.0001 \\[1em] \Rightarrow (10)^{\dfrac{1}{y}} = \dfrac{1}{10^4} \\[1em] \Rightarrow (10)^{\dfrac{1}{y}} = 10^{-4} \\[1em] \Rightarrow \dfrac{1}{y} = -4 \\[1em] \Rightarrow y = -\dfrac{1}{4}.

Substituting value of x and y in 2-x.(16)y we get,

⇒2−1.(16)−14⇒2×(24)−14⇒2×24×−14⇒2×2−1⇒2×12⇒1.\Rightarrow 2^{-1}.(16)^{-\dfrac{1}{4}} \\[1em] \Rightarrow 2 \times (2^4)^{-\dfrac{1}{4}} \\[1em] \Rightarrow 2 \times 2^{4 \times -\dfrac{1}{4}} \\[1em] \Rightarrow 2 \times 2^{-1} \\[1em] \Rightarrow 2 \times \dfrac{1}{2} \\[1em] \Rightarrow 1.

Hence, 2-x.(16)y = 1.

Question 39

If 3x + 1 = 9x - 2, find the value of 21 + x.

Answer

Given,

⇒ 3x + 1 = 9x - 2

⇒ 3x + 1 = (32)x - 2

⇒ 3x + 1 = 32(x - 2)

⇒ 3x + 1 = 32x - 4

⇒ x + 1 = 2x - 4

⇒ 2x - x = 1 + 4

⇒ x = 5.

Substituting value of x in 21 + x we get,

⇒ 21 + x = 21 + 5 = 26 = 64.

Hence, 21 + x = 64.

Question 40

Solve the following equations:

(i) 3(2x + 1) - 2x + 2 + 5 = 0

(ii) 3x = 9.3y, 8.2y = 4x.

Answer

(i) Given,

⇒ 3(2x + 1) - 2x + 2 + 5 = 0

⇒ 3.2x + 3 - 2x.22 + 5 = 0

⇒ 3.2x - 4.2x + 3 + 5 = 0

⇒ -2x + 8 = 0

⇒ 2x = 8

⇒ 2x = 23

⇒ x = 3.

Hence, x = 3.

(ii) Given,

⇒ 3x = 9.3y

⇒ 3x = 32.3y

⇒ 3x = 32 + y

⇒ x = y + 2 ......(i)

Given,

⇒ 8.2y = 4x

⇒ 23.2y = (22)x

⇒ 23 + y = 22x

⇒ 2x = y + 3 .......(ii)

Subtracting (i) from (ii) we get,

⇒ 2x - x = (y + 3) - (y + 2)

⇒ x = 1.

Substituting value of x in (i) we get,

⇒ 1 = y + 2

⇒ y = -1.

Hence, x = 1 and y = -1.

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