Question

A parabola has a vertex at (-1, 0) and opens down. What is the equation of the parabola?


A.) y = -x^2 - 1

B.) y = -(x - 1)^2

C.) y = -(x + 1)^2

Answer 1

C

Answer 2

Remember vertex form of a parabola:
\[y=a(x-h)^2+k\] where (h,k) is the vertex. Plug some values in!
Since nothing else is specified and no graph is given, it's safe to assume that a is 1. But the graph opens down, so it must be -1.

Answer 3

?

Answer 4

You're given the vertex as a coordinate pair, (-1,0). In vertex form, the vertex has coordinates (h,k). That means that h = -1 and k = 0. You can just plug those into the formula thing, and set a=-1 because it opens down. So yes, C is your answer.

Answer 5

Thanks, y'all!:)