Answer
$$x=3\pm3\sqrt3$$
Work Step by Step
We first check that the function is in the form $ax^2+bx+c$. Then, using the quadratic formula, we obtain:
$$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$$
$$x=\frac{-6\pm \sqrt{(6)^2-4(1)(-18)}}{2(1)}$$
$$x=3\pm3\sqrt3$$
