$\left|-4\right|-\left|-4\right|$

$t^2+19t-20<0$

$-4\left(y+2\right)^2$

$\left(-23\right)-\left(-12\right)-\left(5\right)+\left(-9\right)-\left(-3\right)+\left(2\right)-\left(6\right)-\left(-1\right)+\left(-4\right)+\left(7\right)-\left(8\right)-\left(-11\right)$

$-16n=-144$

$b^4c^2\:-\:16b^2$

$\lim_{x\to0}\left(\frac{6x^3\tan9x}{12x^2-12x^2\cos^2x}\right)$