Your problem looks like this

To make this problem easier, we need to simplify these square roots
can be simplified
Here's how :
The factors of 45 are 9 and 5
9 is a perfect square root, but 5 is not
Think of the problem like this

The square root of 9 is 3, but 5 has no perfect square root
Now
is simplified to

Now let's solve the problem, because we have a common square root of 5
- 4\sqrt{5}[/tex]
Our final answer is

Feel free to ask questions if you are confused! Hope I helped :)