$-3b+\left(-3a\right)+4a$

$\left(zy^{-2}x\right)\left(-\frac{1}{5}x^2z^{-3}y\right)$

$\lim_{x\to-\infty}\left(-5x^5-8x\right)$

$\log\left(\frac{x}{\sqrt[6]{8-x}}\right)$

$\left(yx^2+yx-x\right)\left(yx+x-yx^2\right)$

$\left(x^3+3\right)^2+2\left(x^3+3\right)-15$

$dy\:+\:\left(-2y\:-\:e^{3x}\right)dx=0$