Question:
Find the quadratic polynomial, the sum of whose zeros is 0 and their product is −1. Hence, find the zeros of the polynomial.
Solution:
Let $\alpha$ and $\beta$ be the zeros of the required polynomial $f(x)$.
Then $(\alpha+\beta)=0$ and $\alpha \beta=-1$
$\therefore f(x)=x^{2}-(\alpha+\beta) x+\alpha \beta$
$=>f(x)=x^{2}-0 x+(-1)$
$=>f(x)=x^{2}-1$
Hence, the required polynomial is $f(x)=x^{2}-1$.
$\therefore f(x)=0=>x^{2}-1=0$
$=>(x+1)(x-1)=0$
$=>(x+1)=0$ or $(x-1)=0$
$=>x=-1$ or $x=1$
So, the zeros of $f(x)$ are $-1$ and 1 .