Answer
$$x=5/14, -2.5$$
Work Step by Step
When given the choice to use any method, the quadratic formula is a good choice because it will always work.
We first check that the function is in the form $ax^2+bx+c$. Then, using the quadratic formula, we obtain:
$$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$$
$$x=\frac{-60\pm \sqrt{(60)^2-4(28)(-25)}}{2(28)}$$
$$x=5/14, -2.5$$
