$\frac{4x}{5x+1\right)\left(x+4\right)}-\frac{3x}{\left(5x+1\right)\left(x-3\right)}$

$-8x^2-2x=0$

$\lim_{x\to4}\left(\frac{x^2-5}{x^2-x-12}\right)$

$\frac{dy}{dx}=-2y+1$

$-\frac{4}{7}f+\left(-\frac{2}{7}f\right)+\frac{1}{7}$

$u+1=16$

$\left(50\right)\left(-30\right)$