$2\cdot1+\left(-1\right)\cdot\left(-3\right)$

$\frac{5}{x+3}+\frac{1}{x^2-9}$

$\frac{\left(36x^2+9\right)}{\left(6x+3\right)}$

$2x\cdot8y^2$

$3x-8\le\:23\quad\:$

$\int\frac{\cos\left(x\right)}{\tan\left(x\right)}dx$

$\left(\frac{1}{2}a^2+8\right)\left(\frac{1}{2}a^2-4\right)$