Answer
$$ y'= -(2x+3)^{-3/2} .$$
Work Step by Step
Given $ y=\sqrt{2x+3}$, then we have
$$ y'= \frac{2}{2\sqrt{2x+3}} = \frac{1}{\sqrt{2x+3}}=(2x+3)^{-1/2},$$
and the seond derivative $ y''$ is given by
$$ y'=-\frac{1}{2} (2x+3)^{-3/2} (2)=-(2x+3)^{-3/2} .$$
