$\lim_{x\to0}\left(\frac{arctx-x}{x^2}\right)$

$5\sin\left(x\right)=0$

$x^2-3x\le0$

$f\left(x\right)=\frac{12-4x^2}{2x\left(senx\right)}$

$2x+6=20$

$b\left(t\right)\:=\:7.5\:+\:10.5\:sin\left(\frac{2\pi}{63}0\right)$

$3\left(5x\left(2-3x\right)+7\left(3-2\left(x-4\right)\right)\right)$