Answer
$x \lt -2$ or $x \gt 6$.
Work Step by Step
Given $x^2 -4x\gt 12$. Rewrite as: $x^2-4x -12 \gt 0$. Then make a table of values:
Notice that $x^2-4x -12 \gt 0$ when $x \lt -2$ or $x \gt 6$.
The solution of the inequality is $x \lt -2$ or $x \gt 6$.
