The Zero Product Property

Example:

Suppose you want to solve the equation

$x^2+x-20=0$ .

You can factor the left side as:

$(x+5)(x-4)=0$

Now, by the zero product property, either

$x+5=0$   or   $x-4=0$ ,

which means either $x=-5$ or $x=4$ . These are the two solutions of the equation.