$\arctan\left(e^{-\infty}\right)$

$\frac{x+x^2}{3-5x^2}$

$\frac{\sec^4\left(\theta\right)}{cot^2\left(\theta\right)csc^5\left(\theta\right)}$

$4x^2+4x^2-8x^2$

$\frac { 12 n ^ { 3 } - 8 n } { 2 n }$

$\left(5^{\frac{2}{3}}\right)\left(9x^6+4x^{\frac{1}{5}}-x^{\frac{1}{2}}\right)$

$4a^2-12ab+ab^2$