Question

IS THE FOLLOWING QUESTION OF CLASS 10 CBSE MATH 2019 SET 3 CORRECT? If 2/3 and -3 are the zeroes of the polynomial ax^2+7x+b then find a and b.

Answer 1

Given that,

2/3 and -3 are the zeroes of the polynomial $ax^2+7x+b$.

To find,

The value of a and b.

Solution,

If the general form of polynomial is $ax^2+bx+c$ then,

Sum of zeros is $\dfrac{-b}{a}$

In this case,

$\dfrac{2}{3}+3=\dfrac{-7}{a}$

$\dfrac{-7}{3}=\dfrac{-7}{a}$

a = 3 ....(1)

Product of zeros is $\dfrac{c}{a}$

$\dfrac{2}{3}\times -3=\dfrac{b}{a}$

$-2=\dfrac{b}{3}$ (From eq (1))

b = -6

So, the value of a and b is 3 and -6 respectively.