I'm pretty sure I'm doing this correctly, but I'm still getting a wrong answer. Any help would be appreciated.

Find the derivative of the function. Simplify if possible.

I'm getting:

$\displaystyle (\frac{1}{1+(x+\sqrt{1+x^2})^2})\times(1+\frac{1}{ 2\sqrt{1+x^2}})\times2x$