$\lim_{x\to\infty}\left(\frac{\tan\left(x\right)}{\frac{21}{2x-\pi}}\right)$

$\frac{1}{1-sec\left(x\right)}-\frac{1}{1+sec\left(x\right)}=-2cot^2\left(x\right)$

$\int\frac{5x+3}{x\left(x+1\right)}dx$

$\left(y^2-3y\right)\left(y^2+3y\right)$

$\left[2x-3\right]<x+2$

$\left(f+1\right)\left(x^2+1\right)=x\frac{df}{dx}$

$-6a+4b+11c-4c-4b+7a-7b-15c-a$