$\lim_{x\to-1}\left(\frac{3x^4+5x^3+x+3}{x+1}\right)$

$\int_8^{20}\left(\frac{1}{x\sqrt{x^2-25}}\right)dx$

$6a^2+3a+7a^3+2a+5z^2-2a^3$

$\int\left(6x^4\sqrt{x^2+9}\right)dx$

$\frac{x-4}{x+2}=0$

$\lim_{x\to\infty}\left(e^x\cdot\ln\left(1+e^{-x}\right)\right)$

$\frac{x^4+2}{x^2+5x+3}$