$\int_9^{\infty}\left(\frac{1}{x}\right)dx$

$\frac{\sin^2x-\tan^2x}{\csc^2}$

$\log\left(2x\right)-\log\left(x-4\right)=1$

$\frac{5}{\sqrt{-3}}\left(\frac{\sqrt{-3}}{\sqrt{-3}}\right)$

$\lim_{x\to-1}6x^4-x^3+3x^2-5x+9$

$8x+21-x=7\left(x+3\right)$

$17ab+18\cdot y-13ab-12\cdot y$