$\lim_{x\to0}\left(\frac{x^a-ax+a-1}{\left(x-1\right)^2}\right)$

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

$\frac{a^2+ab}{a^2-ab}$

$2a-b+3a\left(2a-b\right)$

$\frac{2x^4-7x^3-14x+8}{x-4}$

$\frac{-52abc}{-4ab}$

$\lim_{x\to17}\left(\frac{x^2-\pi x+\sin x}{-\sin x}\right)$