What is the equation in vertex form?

Question

Find the equation, written in vertex form, of a parabola that has a vertex of (3,-1) and a y-intercept of (0,-8)

 

Answer 1

The vertex form of a parabola is y = a(x-h)²+k, where (h,k) is the vertex.

 

So, we have y = a(x-3)²+(-1)

 

Since (0,-8) is a point on the graph, -8 = a(0-3)²-1

 

                                                   -7 = 9a    a = -7/9

 

Equation of parabola:  y = (-7/9)(x-3)² - 1