am trying to solve for x in this equation

$\displaystyle x^2-\mid x \mid - 12 < 0$

$\displaystyle \mid x \mid <12-x^2$

$\displaystyle \mid x \mid^2 >{(12-x^2})^2$ squaring both sides

i end up with $\displaystyle x^4 - 24x^2+144=0$ can i get some helf solving for x. that if what i did was correct.