Answer
$$n=6,\:n=-2$$
Work Step by Step
The quadratic formula states:
$$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$$
Thus, solving the equation, we find:
$$n=\frac{-\left(-4\right)\pm \sqrt{\left(-4\right)^2-4\cdot \:1\left(-12\right)}}{2\cdot \:1} \\ n=6,\:n=-2$$