How to find the width of a parabola at a a certain level?

Question

The equation of my parabola is x²=-8(y-12). Its vertex is at (0,12). Since it opens downwards, it touches the x axis. What should I do to find the width of the opening that touches the x axis? What equation should I use? Thank you

Answer 1

The easiest way to do that is to plug y = 0 into the equation. That will give you two possible values for x. You simply subtract those two x values to get the width of the parabola.