The vertex of this parabola is at (-5,-2). when the x-value is -4, the y-value is 2. what is the coefficient of the squared expression in the parabola's equation
Accepted Solution
A:
Vertex: (-5,-2); parabola opens up;
General form of the equation for a vertical parabola opening up is:
y-k = a(x-h)^2; knowing that the vertex is at (-5,-2), we can write:
y+2 = a(x+5)^2. We need to find the value of the coefficient a.
From the graph we see that y is 10 when x is approx. -1 3/4 (or -7/4).
subst. these values into y+2 = a(x+5)^2, we get:
10 + 2 = a(-7/4 + 5)^2, or 12 = a(13/4)^2, or 1 = a(169/16).
Solving for a: a = 16/169 = 0.09, or approx 16/160, or 1/10. Unfortunately, this is not close to any of the four answer choices.
I thought it best to try again, and fortunately my second try was correct:
10+2 = a(13/4)^2, or (169/16)a. Thus, 12 = a(169/16)
12 Solving for a: a = ------------- = 1.14. The answer choice closest to this is 1. 169/16