$\left(-1+\frac{4x}{z}\right)^2$

$\left|-12\right|+\left|45\right|$

$\lim_{x\to\infty}\left(\frac{19x}{19x+9}\right)^{2x}$

$xy'+\:3y=x^2-1$

$4ab-3bc$

$1000\lim_{x\to\infty}\left(1+\frac{0.09}{x}\right)^x$

$\ln\left(\cos\left(y\right)\right)dx+x\tan\left(y\right)dy=0$