$\frac{-x\left(y-1\right)}{-5y\left(x-4\right)}$

$-\frac{16^0x^9y^3}{96x^4y^5}$

$\frac{x^{6}+y^{6}}{x+y^{2}}$

$100a^2b^3c-150ab^2c^3+50ab^3c\:-200abc^2$

$\frac{x-\frac{y^{2}}{x}}{\frac{1}{y}-\frac{1}{x}}$

$\left(4+y\right)\left(4-y\right)$

$\int e^x+20\left(1+x^2\right)-1dx$