# Math Help - Second Derivative

1. ## Second Derivative

I think my answer is wrong for this problem. Iv'e work is several times and come up with this.

Find $f(x)''$if $f(x)=\sqrt{2x+5}$

My answer is $\frac{(2x+5)^{-1/2}}{(2x+5)^{5/2}}$

2. Answer is $-\frac{1}{(2x+5)^{\frac{3}{2}}}$
$f'(x) = \frac{1}{(2x+5)^{\frac{1}{2}}}$
$f''(x) = -\frac{1}{(2x+5)^{\frac{3}{2}}}$