# Math Help - factor problem.

1. ## factor problem.

Im toward the end of this problem im practicing...

finding the domain of this function

the answer is x cant be -5 or -4, and i factored it all the way to this point....
but i dont see how they get -5 and -4.... i know its something easy im missing

2. So you factored $x^2 + 9x + 20$ and you got $(x+5)(x+4)$.

So that's what you have on the bottom of your fraction.

Now you can't have 0 on the bottom of a fraction, it's naughty.

So any value of x which makes the bottom zero is not allowed.

So whatever values of x that make $(x+5)(x+4) = 0$ are not in the domain of the function.

Hence the result given.

3. ohhh, gotcha. Thank you