Find the standard form of the equation of the parabola.
-Vertex at the origin, opens downward, focal width $= 18$
A) $x ^ { 2 } = 18 y$
B) $x ^ { 2 } = - 18 y$
C) $y ^ { 2 } = - 4.5 x$
D) $y ^ { 2 } = 18 x$

Question

Quizplus · Accepted Answer

The standard form of a parabola opening downward with the vertex at the origin is $y = -\frac{1}{4p}x^2$, where $4p$ is the focal width. Given the focal width is 18, $p = -\frac{18}{4} = -4.5$. Thus, the equation becomes $x^2 = -18y$.

Find the Standard Form of the Equation of the Parabola =18= 18=18

Find the Standard Form of the Equation of the Parabola $= 18$