Question

What are the zeroes of the polynomial equation? f(x) = x^2+9x+20

Answer 1

Zeroes are when f(x)=0
0=x^2+9x+20
factor
0=(x+4)(x+5)
set each to zero
x+4=0
x=-4
x+5=0
x=-5

zeroes are f(-5) and f(-4)

Answer 2

$x^2+9x+20=0\\ x^2+4x+5x+20=0\\ x(x+4)+5(x+4)=0\\ (x+5)(x+4)=0\\ x=-5 \vee x=-4$