$\lim_{x\to\infty}\left(\frac{2-\sqrt{x-3}}{x^2-49}\right)$

$x^2+x^2y-xy^2$

$\int\left(\frac{\sqrt{8+\tan\left(x\right)}}{1-\sin^2\left(x\right)}\right)dx$

$\left(5-a^2\right)^2$

$\int\left(\frac{2x-1}{x-1}\right)dx$

$3mn+4m+2mn$

$\frac{sec\left(u\right)}{\sec\left(u\right)-1}=\frac{1}{1-cos\left(u\right)}$