Question

A parabola opening up or down has vertex (0, -2) and passes through (8, -18). Write its

equation in vertex form.
Simplify any fractions.

Answer 1

f(x) = -1/4(x - 0)^2 - 2

Explanation:

vertex form:

f(x) = a(x - h)^2 + k

1) put the vertex in the equation, ( (h, k) is the vertex)

f(x) = a(x - 0)^2 - 2

2) plug in the point (8, -18) to find the value of a

-18 = a(8 - 0)^2 - 2

-18 = a(64) - 2

-16 = a(64)

-16/64 = a

-1/4 = a

3) plug in the value of a into the equation

f(x) = -1/4(x - 0)^2 - 2