$1-\frac{6}{x+7}$

$\left(2\sqrt{x}-3\right)\left(5\sqrt{x}+8\right)$

$3f\:+\:f\:+\:2f\:-\:8f\:+\:4f\:+\:3f$

$4x^4-4x$

$\lim_{x\to\frac{\pi}{2}}\left(\left(\cos\left(x\right)\right)\cos\left(\tan\left(6x\right)\right)\right)$

$\frac{d^2}{dx^2}\left(e^{-3x}\right)$

$\frac{x^2-3}{2x-4}$