## Precalculus: Mathematics for Calculus, 7th Edition

(-$\infty$,-3) $\cup$ (6,$\infty$)
$x^{2}$ $\gt$ 3(x+6) $x^{2}$ $\gt$ 3x+18 $x^{2}$ -3x -18 $\gt$ 0 (x-6)(x+3) $\gt$ 0 From factored trinomial we can see that factors are zero when x=-3 or x=6, endpoints don't satisfy the inequality. Plug values from intervals to decide which of them satisfy the inequality.