$\lim_{x\to0}\left(\frac{2x^2}{5x^2+1}\right)$

$x^2\ln\left(x\right)dx=\frac{\left(y+1\right)^2}{y}dy$

$\int\frac{1}{x\sqrt{x^2-225}}dx$

$\frac{7x^2-3x^4+1}{x-1}$

$\left(-9\right)\left(-5\right)\left(-8\right)\left(-7\right)$

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

$\left(1+\frac{lny}{x}\right)dx+\left(1+\frac{lnx}{y}\right)dy=0$