Question

What is the equation in vertex form of the quadratic function with a vertex at (-1, -4) that goes through (1, 8)?

Answer 1

Answer:

y = 3(x+1)^2 - 4

Step-by-step explanation:The general form of the equation of a quadratic function whose vertex is (h,k) and whose leading coefficient is a is:

y - k = a(x-h)^2, or

y      = a(x-h)^2 - k

Substituting the coefficients of the vertex (-1, -4), we get:

y      = a(x + 1)^2 - 4

Substituting the coordinates of the given point, (1,8), we get:

8      = a(1+1)^2 - 4, which simplifies to:

8      = a(2)^2 - 4, or

8  = 4a - 4.  Then 4a = 12, and a = 3.

Thus, the desired equation is y = 3(x+1)^2 - 4 (answer j).