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Mathematics

Verify whether the following are zeroes of the polynomial, indicated against them.

(i) p(x) = 3x + 1, x = 13-\dfrac{1}{3}

(ii) p(x) = 5x - π, x = 45\dfrac{4}{5}

(iii) p(x) = x2 - 1, x = 1, -1

(iv) p(x) = (x + 1)(x - 2), x = -1, 2

(v) p(x) = x2, x = 0

(vi) p(x) = lx + m, x = ml-\dfrac{m}{l}

(vii) p(x) = 3x2 - 1, x = (13)-\Big(\dfrac{1}{\sqrt{3}}\Big), (23)\Big(\dfrac{2}{\sqrt{3}}\Big)

(viii) p(x) = 2x + 1, x = 12\dfrac{1}{2}

Polynomials

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Answer

(i) p(x) = 3x + 1

Putting x = 13-\dfrac{1}{3} we get,

p(13)\text{p}\Big(-\dfrac{1}{3}\Big) = 3(13)3\Big(-\dfrac{1}{3}\Big) + 1

= -1 + 1

= 0

Hence, x = 13-\dfrac{1}{3} is zeroes of this polynomial.

(ii) p(x) = 5x - π

Putting x = 45\dfrac{4}{5} we get,

p(45)=5(45)π\text{p}\Big(\dfrac{4}{5}\Big) = 5\Big(\dfrac{4}{5}\Big) - \pi

= 4 - π

Hence, x = 45\dfrac{4}{5} is not a zeroes of this polynomial.

(iii) p(x) = x2 - 1

Putting x = 1 we get,

p(1) = (1)2 - 1

= 0

Putting x = -1 we get

p(-1) = (-1)2 - 1

= 1 - 1

= 0

Hence, x = 1, -1 is zeroes of this polynomial.

(iv) p(x) = (x + 1)(x - 2)

Putting x = -1 we get,

p(1) = (-1 + 1)(-1 - 2)

= 0 x (-3)

= 0

Putting x = 2 we get,

p(2) = (2 + 1)(2 - 2)

= 3 x 0

= 0

Hence, x = -1, 2 are the zeroes of this polynomial.

(v) p(x) = x2

Putting x = 0 we get,

p(0) = (0)2

= 0

Hence, x = 0 is the zero of this polynomial.

(vi) p(x) = lx + m

Putting x = -ml\dfrac{m}{l} we get,

p - (ml)=lx(ml)\Big(\dfrac{m}{l}\Big) = l x -\Big(\dfrac{m}{l}\Big) + m

= -m + m

= 0

Hence, x = ml-\dfrac{m}{l} is the zero of this polynomial.

(vii) p(x) = 3x2 - 1

Putting x = 13-\dfrac{1}{\sqrt{3}} we get,

p-(13)\Big(\dfrac{1}{\sqrt{3}}\Big) = 3 x -(13)\Big(\dfrac{1}{\sqrt{3}}\Big)2 - 1

= 3 x 13\dfrac{1}{3} - 1

= 1 - 1

= 0

Putting x = 23\dfrac{2}{\sqrt{3}} we get,

p (23)\Big(\dfrac{2}{\sqrt{3}}\Big) = 3 x (23)\Big(\dfrac{2}{\sqrt{3}}\Big)2 - 1

= 3 x 43\dfrac{4}{3} - 1

= 4 - 1

= 3

Hence, x = 13-\dfrac{1}{\sqrt{3}} is zeroes of polynomial but x = 23\dfrac{2}{\sqrt{3}} is not a zeroes of this polynomial.

(viii) p(x) = 2x + 1

Putting x = 12\dfrac{1}{2} we get,

p(12)\Big(\dfrac{1}{2}\Big) = 2 x 12\dfrac{1}{2} + 1

= 1 + 1

= 2

No, x = 12\dfrac{1}{2} is not the zeroes of this polynomial.

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