Solution: The standard form of a parabola with vertical axis is $ y = \frac14px^2 $. The focus is at $ (0, p) $, so $ p = 5 $. The width of 20 units implies the parabola passes through $ (10, 5) $. Substituting: $ 5 = \frac120(100) \Rightarrow 5 = 5 $, which holds. Thus, the equation is $ y = \frac120x^2 $. \boxed{y = \dfrac120x^2} - Get link 4share