$81+18x+x^{2}=0$

$\int\left(sin^8\frac{x}{7}cos\frac{x}{7}\right)dx$

$\lim_{x\to\pi}\left(\frac{sin\left(x+\pi\right)}{cos\left(x-\frac{\pi}{2}\right)}\right)$

$\lim_{x\to\infty}\left(1+\frac{6}{x^4}\right)^{\frac{x}{4}}$

$\int\:\:\frac{6}{x^3-4x^2+3x}dx$

$\lim_{x\to4}\left(\frac{x^3+125}{x^2-25}\right)$

$\left(3x^4-9x^1\right)\left(7-x\right)$