$14m^2n-7mn$

$-4x-20+2x-18$

$\left(-982\right)+\left(-1021\right)+\left(-654\right)+\left(257+1500\right)+\left(-635\right)$

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

$\frac{tan^2x-sin^2x}{sin^2x}=5$

$\left(50-4y\right)dx=e^{\frac{x}{5}}dy$

$\left(3xy-9\right)\left(3xy+9\right)$