$$\displaystyle\int{ \frac{ { x }^{ 3 } }{ \sqrt{ { 5 }^{ 2 } + { x }^{ 2 } } } }d x$$
$\sqrt{x^{2}+25}x^{2}-\frac{2\left(x^{2}+25\right)^{\frac{3}{2}}}{3}+С$
$\frac{x^{3}}{\sqrt{x^{2}+25}}$
