$\csc^{2}\theta\cdot\tan^{2}\theta-1=\tan^{2}\theta$

$\frac{15y^3\left(x-9\right)^3}{5y^4\left(x-9\right)^2}$

$10x+8y-3x+4z-3x+6z-7y$

$2x-\left(5x+3\right)=7-\left(3x-2\right)$

$\frac{xy\sqrt[3]{y^2}}{2}$

$2\sin\left(\pi+x\right)-\cos\left(x+\pi\right)$

$\lim_{x\to7}\left(\frac{3-\sqrt[5]{250-x}}{7-x}\right)$