The zeros of the polynomial
Question:

The zeros of the polynomial $x^{2}-2 x-3$ are

(a) −3, 1
(b) −3, −1
(c) 3, −1
(d) 3, 1

Solution:

(c) $3,-1$

Let $f(x)=x^{2}-2 x-3=0$

$=x^{2}-3 x+x-3=0$

$=x(x-3)+1(x-3)=0$

$=(x-3)(x+1)=0$

$=x=3$ or $x=-1$