$6\le-\frac{5}{9}+x$

$\frac{d^2}{dx^2}\left(\frac{4+x}{4-x}\right)$

$\int\frac{3x^2+7x-4}{x^3+4x^2}\:dx$

$\left(-3a^2+2\right).\left(a^2+4\right)$

$x'=\left(4+x\right)\cdot\left(5+t\right)$

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

$\tan\left(\arccos\left(x\right)\right)$