This is the classic difference of two squares. Use the following model to factor:
For this one, think of two numbers whose product is -5 and whose sum is 4. You'll discover that there is only one solution to that question: 5 and -1
Try expanding everything and collecting terms to get a neat quadratic expression. Then, we'll try to factor it. Or, better still, do what stapel suggests in her post. It's cleaner.
Observe that the expression has a common monomial factor.
This is a strange little booger!
Let x = (9+5), then
Now back substitute to get
I really don't know what you might want to do next since everything here is numbers.