$x^4\left(2x-3x^{-2}\right)$

$\sec\left(x\right)^2=4\tan\left(x\right)-2$

$x^2+6x+13<0$

$9y^2+4z^2-x^2-18y-16z+4x+21=0$

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

$4x\left(-5\right)$

$43mx3+7mx-17mx3-13mx$