$\left(-3x^2yz^4\right)\cdot\left(-7xy^3z^6\right)$

$\left(a^2.b\right)^4.\left(a.b\right)^{-2}$

$\frac{\:\:x^4-7x^3+18x^2-22x+12}{x-1}$

$\frac{dy}{dt}=\frac{y+13}{5t+6}$

$36m^2-81n^2$

$\lim_{x\to0}\left(\frac{x^3tan\left(x\right)}{sin^4\left(x\right)}\right)$

$\left(\frac{2}{3}+b\right)^2$