$$\frac{a^{2}+x^{2}}{\sqrt{a^{2}-x^{2}}}$$
$\frac{x^{2}+a^{2}}{\sqrt{a^{2}-x^{2}}}$
$\frac{x\left(3a^{2}-x^{2}\right)}{\left(a^{2}-x^{2}\right)^{\frac{3}{2}}}$
