Help! dy/dx of inverse trig functions

[ugly_boy]

I must be missing something here. The derivatives of the inverse trig functions seemed pretty straightforward but none of my answers are even close to the ones in the book. Hopefully somebody can show me how to work through this one and I can try to do the rest once I see a good example.

Images after the cut.

Differentiate



Knowing that


and


This is what I came up with:


But the book gives:


I realize that I could have factored (2x+1)2 but even if I had done that my answer isn't even close.