Question:
Find the quadratic polynomial, the sum of whose zeros is $\left(\frac{5}{2}\right)$ 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 $(\alpha+\beta)=\frac{5}{2}$ and $\alpha \beta=1$
$\therefore f(x)=x^{2}-(\alpha+\beta) x+\alpha \beta$
$=>f(x)=x^{2}-\frac{5}{2} x+1$
$=>f(x)=2 x^{2}-5 x+2$
Hence, the required polynomial is $f(x)=2 x^{2}-5 x+2$.
$\therefore f(x)=0=>2 x^{2}-5 x+2=0$
$=>2 x^{2}-(4 x+x)+2=0$
$=>2 x^{2}-4 x-x+2=0$
$=>2 x(x-2)-1(x-2)=0$
$=>(2 x-1)(x-2)=0$
$=>(2 x-1)=0$ or $(x-2)=0$
$=>x=\frac{1}{2}$ or $x=2$
So, the zeros of $f(x)$ are $\frac{1}{2}$ and 2 .