$f\left(x\right)=\frac{1}{\left(x^3-2x^2-7x\right)^4}$

$\left(\frac{2x^3}{x-4}\right)\left(\frac{\left(x^3-64\right)}{2x^2}\right)$

$xy-x^2y+x^3y^2$

$-4x^3y\left(6x-8y^2+5x^2y^2\right)$

$\int\frac{1}{\left(x+9\right)\left(x+7\right)}dx$

$\log x+\log\left(3x-5\right)=\log2$

$-x^2+9x+20,25$