Question

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

Answer 1

`-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`.