How do you factor -9a^2-9a?

1 Answer
Nov 24, 2015

-9a(a+1)

Explanation:

What is a common factor of the equation?
First lets look at 9

The two numbers -9 and -9 both have a common factor of -9, so we can take out a -9 by dividing the equation by -9 and placing it on the outside of the brackets.

Factoring out -9

-9((cancel(-9)a^2)/cancel(-9)+(cancel(-9)a)/cancel(-9))

New equation: -9(a^2+a)

Now lets look at a

The common factor of a^2 and a is a. Take out a by dividing the inside of the brackets by a and placing it on the outside

Factoring out the a
-9a((a^cancel2)/cancela+cancela/cancela)
New equation: -9a(a+1)

Note: Keep in mind that a/a is 1, not zero, because 1/1 is not zero either, so we have to keep a 1 after cancelling out a/a.