It's also a very similar technique that we use oftentimes to get rid of complex numbers usually in denominators. But if you multiply this out, and I encourage you to do it, you notice this has the pattern that you learned in algebra class. This is the difference of squares. Something minus something times something plus something. So the first term is going to be the first something squared. So square root of x plus 4 squared is x plus 4. The second term is going to be the second something or you're going to subtract the second something squared.