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

$\int\left(cos\right)^6x\:dx$

$\lim_{x\to0}\left(\frac{2x^2-3x}{5x^2+3}\right)$

$\int\frac{1}{\sqrt{-4x-9}}dx$

$\left(48f^2-27f^8\right)^2$

$\frac{dx}{dt}=\left(10-x\right)\left(50-x\right)$

$\left[e^xy-3e^x\left(e^x+1\right)^2\right]dx+\left(e^x+1\right)dy=0$