$1-3\left(\infty\right)\cdot\frac{1}{\infty^2}$

$\int\left(\frac{9x+7}{x^2+1}\right)dx$

$\frac{\sin\left(x\right)\cos\left(x\right)}{1-\sin^2\left(x\right)}$

$\frac{1}{81}x^2-4>0$

$\lim_{x\to.999}\left(\frac{x+3}{\left(x-1\right)^2}\right)$

$\frac{dx}{dy}=4\left(x^2-1\right)$

$y=\:x^{\left(-3\right)}+x^2-5\:\:\:\:$