Q. 44.0( 44 Votes )

The number of polynomials having zeroes as - 2 and 5 is
A. 1
B. 2
C. 3
D. more than 3

Answer :

let - 2 and 5 are the zeroes of the polynomials of the form p(x) = ax2 + bx + c

Sum of the zeroes = -(coefficient of x) ÷ coefficient of x2 i.e.


Sum of the zeroes = - b/a

- 2 + 5 = - b/a

3 = - b/a

b = - 3 and a = 1


Product of the zeroes = constant term ÷ coefficient of x2 i.e.


Product of zeroes = c/a

(- 2)5 = c/a

- 10 = c


Put the values of a, b and c in the polynomial p(x) = ax2 + bx + c

The equation is x2 - 3x - 10

OR

The equation of a quadratic polynomial is given by x2 - (sum of the zeroes)x + (product of the zeroes) where,

Sum of the zeroes = - (coefficient of x) ÷ coefficient of x2 and

Product of the zeroes = constant term ÷ coefficient of x2

Sum of the zeroes = - 2 + 5 and product of the zeroes = (- 2)5

= 3 = - 10

the equation is x2 - 3x - 10

We know, the zeroes do not change if the polynomial is divided or multiplied by a constant

kx2 - 3kx - 10k will also have - 2 and 5 as their zeroes.

As k can take any real value, there can be many polynomials having - 2 and 5 as their zeroes.

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