Question

Find a quadratic polynomial having zeroes equal to 7 and -3 ?

• A.
  $k(x^2-4x-21)$
• B.
  $k(x^2-4x+21)$
• C.
  $k(x^2-3x-21)$
• D.
  $k(x^2-3x+21)$

Answer 1

The correct option is A

$k(x^2-4x-21)$
Let $\alpha$ and $\beta$ be zeroes
$\alpha =7and\beta =-3\Rightarrow S=\alpha +\beta =7+(-3)=4\Rightarrow P=\alpha \beta =7(-3)=-21\text{where S is sum of the roots and P is the product of the roots}\text{Hence, Required quadratic polynomial is}=k[x^2-Sx+P]=k[x^2-4x-21]$
So, option a is correct.