$5sen\:x\:-4\:=\:0$

$2000\cdot\left(0.2\right)^2$

$\left(r-3w\right)\left(r+3w\right)$

$x^2y=0$

$\lim_{x\to\infty}\left(\frac{x\cdot sin\left(\frac{1}{x}\right)}{cos\left(\frac{1}{x}\right)}\right)$

$\left|\left(-7\right)\cdot3\right|^4$

$\lim_{x\to-7}\left(\frac{x^2+1}{\sqrt{x^2-49}}\right)$