$\left(9x^2\:+\:4y^5\right)\:\left(9x^2\:-\:4y^5\right)$

$\lim_{y\to0}\left(\frac{y^2}{\ln\left(\cos\left(y\right)\right)}\right)$

$-2.x^2-11$

$5\left(3+5+4-8-8\right)$

$\lim_{x\to0}\left(\left(1-x\right)^{\frac{8}{x}}\right)$

$\left(8b\:+\:4\right)\left(8b\:-\:4\right)$

$csc\left(x\right)=sec\left(x\right)cot\left(x\right)$