It is a very good idea to learn some LaTex. If I may, I think I know what you mean. Correct me if I am wrong.
\(\displaystyle \L\\f(x)=\sqrt{4x+4}\)
Write an expression for:
\(\displaystyle \L\\(f(1+h)+f(1))(f(1+h)-f(1))\)
If this is indeed what you have, in your equation enter 1+h in for x and 1 in for x and simplify.
For instance, I'll show you one part and you finish.
\(\displaystyle \L\\f(1+h)+f(1)\)
\(\displaystyle \L\\\sqrt{4(1+h)+4}+\sqrt{4(1)+4}\)
Now, do the other, multiply it with this one and simplify.
It'll reduce to something very simple and nice.