Question:
A quadratic polynomial, the sum of whose zeroes is 0 and one zero is 3, is
(a) $x^{2}-9$
(b) $x^{2}+9$
(c) $x^{2}+3$
(d) $x^{2}-3$
Solution:
Since $\alpha$ and $\beta$ are the zeros of the quadratic polynomials such that
$0=\alpha+\beta$
If one of zero is 3 then
$\alpha+\beta=0$
$3+\beta=0$
$\beta=0-3$
$\beta=-3$
Substituting $\beta=-3$ in $\alpha+\beta=0$ we get
$\alpha-3=0$
$\alpha=3$
Let S and P denote the sum and product of the zeros of the polynomial respectively then
$S=\alpha+\beta$
$S=0$
$P=\alpha \beta$
$P=3 \times-3$
$P=-9$
Hence, the required polynomials is
$=\left(x^{2}-S x+P\right)$
$=\left(x^{2}-0 x-9\right)$
$=x^{2}-9$
Hence, the correct choice is (a)