$-4-\left(-9\right)$

$-x^4-8x^2+9$

$\frac{1}{x}|_{i}$

$\frac{180}{6}$

$\frac{\cos\left(x\right)}{1-\tan\left(x\right)}-\frac{\sin\left(x\right)}{\cot\left(x\right)-1}$

$\int_0^{\infty}\left(\frac{e^x}{\left(1+e^x\right)}\right)dx$

$2y\:cos\left(x\right)dx\:+\:3\:sin\left(x\right)\:dy\:=0$