$7a-8b-15a+a+b-4c$

$23y^2\left(3x-14\right)\left(3x+14\right)$

$\lim_{x\to2}\left(\frac{4-x^2}{3x-\sqrt{x^2+5}}\right)$

$\lim_{x\to\infty}\left(1-\frac{12}{x}\right)^{5x}$

$\lim_{x\to infinity}\left(\frac{\sin\left(2x\right)\cos\left(e^{x^2+9}\right)}{x^2+9}\right)$

$\frac{x^3+4x^2-7x-10}{x^2-x-6}$

$\frac{dy}{dx}=xe^{x+2y}$