$\lim_{x\to-2}\left(\frac{3-\sqrt{6x+21}}{x-2}\right)$

$\int\left(-1+x^2\right)\frac{2x+1}{x^2+1}dx$

$-9-s+2-2r+4s+1$

$\left(5x-2\right)\left(-x-5\right)\left(5x+5\right)$

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

$3c^4\left(10c^5-6\right)$

$\left(10x+6b\right).\left(10x-6b\right)$