Find a formula for the quadratic function whose graph has vertex (−2,−1) and y-intercept 6.
Vertex form of the parabola
y = a ( x+2)^2 -1 sub in 0,6 to calculate 'a'
6 = 4a - 1
7 = 4a
a = 7/4
y = 7/4 (x+2)^2 -1 expand and simplify to the form you need (quadratic)
y = 7/4 (x^2 + 4x + 4) -1
y = 7/4 x^2 + 7x +6
A y intercept of 6 means that (0,6) is on the graph
We have the form
y = a ( x - h)^2 + k where x = 0 y = 6 h = -2 and k = -1
We need to solve for a
6 = a ( 0 + 2)^2 - 1
6 + 1 = 4a
7 = 4a
a = 7/4
The function is
y = (7/4) ( x + 2)^2 - 1
y = (7/4) ( x^2 + 4x + 4 ) - 1
y = (7/4) x^2 + 7x + 7 -1
y = (7/4)x^2 + 7x + 6