Question

The vertex of this parabola is at (2, -4). When the y-value is -3, the x-value is -3. What is the coefficient of the squared term in the parabola's equation?A.-1B.-5C.1D.5

Answer 1

a = 1/25

Explanation:

The vertex form of the parabola is

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

where (h,k) is the vertex

y = a(x-2)^2 -4

We have a point on the parabola (-3,-3) so substitute this into the equation

-3 = a(-3-2)^2 -4

-3 = a(-5)^2 -4

Add 4 to each side

-3+4 = a(25) +4-4

1 = 25a

Divide each side by 25

1/25 = a

y = 1/25(x-2)^2 -4