$-5ab+3ab-4ab+ab$

$4\cdot\left(x+5\right)=\left(3x+1\right)\cdot3+2$

$\left(-6\right)^2-4\left(3\right)\left(1\right)$

$\lim_{x\to\infty}\left(\frac{x^2-x-1}{x^2+5x^7+3x^5}\right)$

$\int\frac{1}{\left(x+5\right)\left(x+6\right)}dx$

$\frac{x}{8}=20$

$\frac{dy}{dx}=\frac{2+\sqrt{x}}{7+\sqrt{y}}$