$\left(20c^2-8d^7\right)^2$

$\left|7\right|-9$

$f\left(x\right)=x\left(x^{-1}+x^{-2}+x^{-3}\right)^{-4}$

$\lim_{x\to-2}\left(\frac{1}{\sqrt{4-x^2}}\right)$

$\frac{dy}{dz}\left(z^2-8x^4y^{-\frac{1}{2}}=208x^{10}y^2-xz\right)$

$1-a<0$

$\lim_{x\to0}\left(13sin\left(9x\right)ln\left(9x\right)\right)$