$2\:\cdot\:cos^2\left(x\right)\:-\:9\:\cdot\:cos\:\left(x\right)\:=\:5$

$-7\left(-4\:-\:2\:+\:3\right)$

$\left(2\cdot\left(y+3\right)\right)\left(y\left(2x-1\right)\right)$

$\frac{\left(8x^2-2y^3\right)\left(8x^2+2y^3\right)}{2}$

$\int\left(\sqrt{x}+1\right)\left(x-\sqrt{x}+1\right)dx$

$y2\left(a-x\right)$

$\int_{-2}^3\left(\frac{21}{x^4}\right)dx$