$\infty7$

$\left(-20x^2+105x\right)\left(x\right)$

$9x\cdot4\:-\:16x\cdot8\:$

$4c-2c\:3\:and\:2c-3$

$\sqrt{64x^4y^{22^2}}$

$\frac{1}{1-\sin^2\left(x\right)}=\tan^2\left(x\right)\left(1+\cot^2\left(x\right)\right)$

$\lim_{x\to5}\left(\frac{x^2-10x+25}{x^2-7x+10}\right)$