$5+\left(-11\right)-\left(-3\right)-\left(+21\right)$

$\left(5-2z\right)\left(5+2z\right)$

$\sin\:^{\left(6\right)}\left(20\right)+\sin\:^{\left(2\right)}\left(20\right)\sin\:^{\left(2\right)}\left(70\right)+\sin\:^{\left(4\right)}\left(20\right)\sin\:^{\left(2\right)}\left(70\right)+\sin\:^{\left(2\right)}\left(70\right)$

$\frac{-74ab+74a^2b}{\left(2x-1\right)^{-1}}$

$2y+10+xy+5x$

$\lim_{x\to-9}\left(\frac{4x}{x+5}\right)$

$\int\frac{-10e^x-36}{e^{2x}+7e^x+12}dx$