f(x) = a(x-h)^2 + k, for a parabola that passes through the point (8,12) and has (6,10) as its vertex:Â
Start with    y =f(x) = a(x-h)2 + k.   We know that (8,12) and (6,10) are both on the graph of the parabola, and that (6,10) is the vertex.  Therefore the following is
true:
Â
 f(x) = y = a(x-6)^2 + 10   =>    12= y = a(8-6)^2 + 10
Then 12 = a(2)^2 + 10, or 2 = a(4), or a = 2/4, or a = 1/2.
Then the equation for this parabola is  y = (1/2)(x-6)^2 + 10.