Correct, you do use the chain rule!

You have probably just done a bunch of chain rule questions? The squareroot bit probably threw you off.

Try writing it as I have here.

Now, the first few lines I wrote the chainnrule in my notation. If it confuses you, let me know.

Next I have pointed out what the overall function is and the function inside the function part is. Now it is just a case of putting in the values. Once you have rewritten the squareroot like I have, it might make more sense to you.

Checking can be done by using Wolfram Alpha, wolframalpha.com.