Karyn T. answered 01/21/18
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For the love of Math! Experienced Math tutor for grades 6-12
The Vertex form of a parabola (quadratic equation) is y = a (x-h)^2 + k, where h and k are the coordinates of the vertex given as (5,0). Plug in (5,0) into the general equation, y = a (x-5)^2 + 0 or y = a (x-5)^2. "a" is the leading coefficient for all forms of a quadratic equation: standard form, vertex form and intercept form.
In this problem, you are given a point on the parabola so you can solve for "a". Plug in the point coordinates (7, -2) into y = a (x-5)^2 to solve for "a", -2 = a (7-5)^2 or a= -1/2.
The final equation for the parabola described in the problem statement is therefore, y = -1/2 (x-5)^2