Answer
$ \frac{x(3x^2+2)}{(x^2+1)^{1/2}}$
Work Step by Step
$2x(x^2+1)^{1/2}+x^2\cdot\frac{1}{2}(x^2+1)^{-1/2}\cdot2x=2x(x^2+1)^{1/2}+\frac{x^3}{(x^2+1)^{1/2}}=\frac{2x(x^2+1)+x^3}{(x^2+1)^{1/2}}=\frac{3x^3+2x}{(x^2+1)^{1/2}}=\frac{x(3x^2+2)}{(x^2+1)^{1/2}}$