Question 28480
Solve by factoring:
{{{x^2-9x = -20}}} First, add 20 to both sides of the equation.
{{{x^2-9x+20 = 0}}} Now factor the left side.

Factoring: The two factors will have the form{{{(x+a)(x+b)}}} where: a+b = -9
and a X b = 20

Try these: a = -4 and b = -5
a+b = (-4)+(-5) = -9
a X b = (-4)(-5) = 20 So these will work.
The factors are:
(x-4)(x-5), so we have:
(x-4)(x-5) = 0 Apply the zero products principle.
x-4 = 0 and/or x-5 = 0
If x-4 = 0, then x = 4
If x-5 = 0, then x = 5

The roots are:
x = 4
x = 5