# Second Derivatives

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• Dec 18th 2012, 08:56 AM
GrigOrig99
Second Derivatives
Having a bit of trouble with this one. Can anyone help me out?

Many thanks.

Q. Find the second derivative of $y=\sqrt{2x+3}$.

Attempt: $y=(2x+3)^{1/2}$
$f'(x)=(1/2)(2x+3)^{-1/2}(2)\rightarrow \frac{1}{\sqrt{2x+3}}$
$f''(x)=(-1/2)(2x+3)^{-3/2}(2)\rightarrow -\frac{1}{\sqrt{(2x+3)^3}}$

Ans: (From text book): $\frac{-1}{2\sqrt{(2x+3)^3}}$
• Dec 18th 2012, 09:01 AM
ebaines
Re: Second Derivatives
Your answer is correct.
• Dec 18th 2012, 09:09 AM
jakncoke
Re: Second Derivatives
Yes, your textbook is wrong
• Dec 18th 2012, 09:37 AM
GrigOrig99
Re: Second Derivatives
Great. Thank you very much.