Question

Which equation has a graph that is a parabola with a vertex at (–1, –1)?

y = (x – 1)2 + 1
y = (x – 1)2 – 1
y = (x + 1)2 + 1
y = (x + 1)2 – 1

Answer 1

D

Explanation:

Answer 2

`y=(x+1)^2-1`

which agrees with the last option listed.

Explanation:

We use the vertex form of a parabola:

`y-y_v=a(x-x_v)^2`

which with the information we have becomes:

`y-y_v=a(x-x_v)^2\\y-(-1)_v=a(x-(-1))^2\\y=a(x+1)^2-1`

Therefore the equation that corresponds to such vertex (-1, -1) is the last one listed among your given answer options.

`y=(x+1)^2-1`