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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)3827.\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)21649.\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:

a1+b1(ab)1\dfrac{a^{-1} + b^{-1}}{(ab)^{-1}}

Answer

Given,

a1+b1(ab)1=(a1+b1)×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, a1+b1(ab)1\dfrac{a^{-1} + b^{-1}}{(ab)^{-1}} = a + b.

Question 3(i)

Simplify the following:

x1y1x1+y1\dfrac{x^{-1}y^{-1}}{x^{-1} + y^{-1}}

Answer

Given,

x1y1x1+y1=(xy)1×1x1+y1=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, x1y1x1+y1=1x+y\dfrac{x^{-1}y^{-1}}{x^{-1} + y^{-1}} = \dfrac{1}{x + y}

Question 3(ii)

Simplify the following:

(4×107)(6×105)8×1010\dfrac{(4 \times 10^7)(6 \times 10^{-5})}{8 \times 10^{10}}

Answer

Given,

(4×107)(6×105)8×1010=4×6×107×1058×1010=24×107+(5)8×1010=24×1028×1010=3×102×1010=3×102+(10)=3×108.\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)(6×105)8×1010=3×108.\dfrac{(4 \times 10^7)(6 \times 10^{-5})}{8 \times 10^{10}} = 3 \times 10^{-8}.

Question 4(i)

Simplify the following:

3ab1+2ba1\dfrac{3a}{b^{-1}} + \dfrac{2b}{a^{-1}}

Answer

Given,

3ab1+2ba1=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, 3ab1+2ba1\dfrac{3a}{b^{-1}} + \dfrac{2b}{a^{-1}} = 5ab.

Question 4(ii)

Simplify the following:

50 × 4-1 + 8138^{\dfrac{1}{3}}

Answer

Given,

50×41+813=1×41+(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, 50×41+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=32n3n=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+125.(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+125.(5)2n5.(5)2n+3(25)n+1=5.(52)n+1(52)(5)2n5.(5)2n+3(52)n+1=5.52n+252+2n52n+452n+2=52n+352n+252n+452n+2=52n.5352n.5252n.5452n.52=52n(5352)52n(5452)=1252562525=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+125.(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:

[843÷22]12\Big[8^{-\dfrac{4}{3}} ÷ 2^{-2}\Big]^{\dfrac{1}{2}}

Answer

Given,

[843÷22]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, [843÷22]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)2342+1=33×2323×2316+1=322215=9415=9604=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)4313=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+34×36+(13)2(3^2)^0 + 3^{-4} \times 3^6 + \Big(\dfrac{1}{3}\Big)^{-2}

Answer

Given,

(32)0+34×36+(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+34×36÷(13)2(3^2)^0 + 3^{-4} \times 3^6 ÷ \Big(\dfrac{1}{3}\Big)^{-2} = 19.

Question 10(ii)

Simplify the following:

(9)523.(5)0(181)12(9)^{\dfrac{5}{2}} - 3.(5)^0 - \Big(\dfrac{1}{81}\Big)^{-\dfrac{1}{2}}

Answer

Given,

(32)523.1(192)12=32×523(92)12=3539=24312=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)523.(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=2722+4=274+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+36×5n+19×5n22×5n\dfrac{5^{n + 3} - 6 \times 5^{n + 1}}{9 \times 5^n - 2^2 \times 5^n}

Answer

Given,

5n+36×5n+19×5n22×5n=5n.536.5n.515n(922)=5n.(5330)5n(94)=125305=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+36×5n+19×5n22×5n\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)23.22÷80]12\Big[(64)^{\dfrac{2}{3}}.2^{-2} ÷ 8^0\Big]^{-\dfrac{1}{2}}

Answer

Given,

[(64)23.22÷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)23.22÷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÷(3n1×9n1)3^n \times 9^{n + 1} ÷ (3^{n - 1} \times 9^{n - 1})

Answer

Given,

3n×9n+1÷(3n1×9n1)=3n×9n+1×13n1×9n1=3n×9n.913n.31×9n.91=931×91=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÷(3n1×9n1)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)222×284263(2)2(22)12×(28)14(26)134(2)2×12×(2)8×14(2)6×1342×22224242.\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:

367×437×937×26722+20+22\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,

367×437×937×26722+20+22367×(22)37×(32)37×2674+1+(12)2367×(2)67×(3)67×2674+1+(14)367+67×(2)67+67(16+4+14)30×202141214421.\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, 367×437×937×26722+20+22=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)1322÷(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)1322÷(64)13(25)25×(22)12×(23)1322÷(26)1322×21×2122÷22221+12222221=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)1322÷(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)2x52x+12×(52)7+2x(53)2x52x+12×514+4x56x52x+12+(14+4x)56x56x2.56x56x2+(6x)52=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)2372n+3(72)n+2((73)n+1)2372n+372n+473×(n+1)×2372n.7372n.7472(n+1)343.72n2401.72n72n+272n(3432401)72n.72205849=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+5481+16+5497+54388+54393498.25\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:

(325)13(32+5)13(\sqrt{32} - \sqrt{5})^{\dfrac{1}{3}}(\sqrt{32} + \sqrt{5})^{\dfrac{1}{3}}

Answer

Given,

(325)13(32+5)13[(325)(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[325]13(27)13(33)133.\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, (325)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:

(x13x13)(x23+1+x23)\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,

(x13x13)[(x13)2+x13.x13+(x13)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)

(x13x13)[(x13)2+x13.x13+(x13)2]=(x13)3(x13)3(x3×13)(x3×13)x1x1x1x.\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, (x13x13)(x23+1+x23)=x1x\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.xn)l.(xn.xl)m.(xl.xm)n=(xmn)l.(xnl)m.(xlm)n=xmlnl.xnmlm.xlnmn=xmlnl+nmlm+lnmn=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)ab.(xb+cxa)bc.(xc+axb)ca\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)ab.(xb+cxa)bc.(xc+axb)ca=(xa+bc)ab.(xb+ca)bc.(xc+ab)ca=x(a2ab+bab2ca+cb).x(b2bc+cbc2ab+ac).xc2ca+aca2bc+ba=xa2ab+bab2ca+cb+b2bc+cbc2ab+ac+c2ca+aca2bc+ba=xa2a2ab+bab2+b2ca+ac+cbbc+cbbcab+baca+acc2+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)ab.(xb+cxa)bc.(xc+axb)ca\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=xlmlm.xmnmn.xnlnl=(x)lmlm.(x)mnmn.(x)nlnl=(x)lmlm+mnmn+nlnl=(x)(lm)n+(mn)l+(nl)mlmn=(x)lnmn+mlnl+nmlmlmn=(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(ab))(a2+ab+b2).(x(bc))(b2+bc+c2).(x(ca))(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)a3b3.(x)b3c3.(x)c3a3xa3b3+b3c3+c3a3x0=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:

(xaxb)a2ab+b2.(xbxc)b2bc+c2.(xcxa)c2ca+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,

(xaxb)a2ab+b2.(xbxc)b2bc+c2.(xcxa)c2ca+a2(x(a(b)))(a2ab+b2).(x(b(c)))(b2bc+c2).(x(c(a)))(c2ca+a2)(x(a+b))(a2ab+b2).(x(b+c))(b2bc+c2).(x(c+a))(c2ca+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+a3xa3+b3+b3+c3+c3+a3x2(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, (xaxb)a2ab+b2.(xbxc)b2bc+c2.(xcxa)c2ca+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,

(a1+b1)÷(a2b2)(1a+1b)÷(1a21b2)(b+aab)÷(b2a2a2b2)(b+aab)×(a2b2b2a2)ab(b+a)b2a2ab(b+a)(ba)(b+a)abba.\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) = abba.\dfrac{ab}{b - a}.

Question 20(ii)

Simplify the following:

11+amn+11+anm\dfrac{1}{1 + a^{m - n}} + \dfrac{1}{1 + a^{n - m}}

Answer

Given,

11+amn+11+anm11+am.an+11+an.am11+aman+11+anam1an+aman+1am+anamanan+am+amam+anan+aman+am1.\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+amn+11+anm\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(a1+b1)=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+zx1y1+y1z1+z1x1=xyz\dfrac{x + y + z}{x^{-1}y^{-1} + y^{-1}z^{-1} + z^{-1}x^{-1}} = xyz

Answer

Given,

x+y+zx1y1+y1z1+z1x1=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+1zxx+y+zz+x+yxyzxyz(x+y+z)x+y+zxyz.\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+zx1y1+y1z1+z1x1\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)

6z=k or 6=k1z\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=k1zk1x+1y=k1z1x+1y=1z1x+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 = 2yzyz.\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=k1zk2x×k1y=k1zk2x+1y=k1z2x+1y=1z2x=1z1y2x=yzyzx2=yzyzx=2yzyz.\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=2yzyz.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)=198=1729=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=103×0.0099102×110=9.9102×110=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.y1.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.y1.z23x^{\dfrac{1}{2}}.y^{-1}.z^{\dfrac{2}{3}} we get,

x12.y1.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.y1.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 a6b43=ax.b2y\sqrt[3]{a^6b^{-4}} = a^x.b^{2y}, find x and y, where a, b are different positive primes.

Answer

Given,

a6b43=ax.b2y(a6b4)13=ax.b2ya63.b43=ax.b2ya2.b43=ax.b2yx=2 and 2y=43x=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(p1+q1)=paqb1(p+q)(1p+1q)=paqb1(p+q)×p+qpq=paqb1pq=paqbp1q1=paqba=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 (p1q2p2q4)7÷(p3q5p2q3)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,

(p1q2p2q4)7÷(p3q5p2q3)5=pxqy(p1q2p2q4)7÷(p2q3p3q5)5=pxqyp7q14p14q28×(p3q5p2q3)5=pxqyq14.q28p14.p7×p15q25p10q15=pxqyq14+28p14+7×p15.p10q25.q15=pxqyq42p21×p25q40=pxqyp4q2=pxqyx=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=44346(13)^{\sqrt{x}} = 4^4 - 3^4 - 6

Answer

Given,

(13)x=44346(13)x=256816(13)x=169(13)x=132x=2x=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)3x+12=3x+1=6x=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=25(2)4x3+13=254x+13=54x+1=154x=16x=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)12x\sqrt{\dfrac{p}{q}} = \Big(\dfrac{q}{p}\Big)^{1 - 2x}

Answer

Given,

pq=(qp)12x(pq)12=(pq)(12x)(pq)12=(pq)(2x1)12=2x12x=1+122x=32x=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:

4x1×(0.5)32x=(18)x4^{x - 1} \times (0.5)^{3 - 2x} = \Big(\dfrac{1}{8}\Big)^x

Answer

Given,

4x1×(0.5)32x=(18)x(22)x1×(510)32x=(123)x22x2×(12)32x=(23)x22x2×(21)32x=23x22x2×22x3=23x22x2+2x3=23x24x5=23x4x5=3x4x+3x=57x=5x=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=0.00110y=1100010y=110310y=103y=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=13332n+n.3233n33m.8=13333n.933n33m.8=13333n(91)33m.8=13333n.833m.8=3333n33m=3333n=33m.3333n=33m+(3)3n=3m33n=3(m1)n=m1m=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=1041y=4y=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,

21.(16)142×(24)142×24×142×212×121.\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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