what is the Quadratic equation if the given Vertex is (0,-2), and the given points within the parabola is (2,0), and (-2,0)? please help!

Question

directrix · Answer

If h and k are the coordinates of the vertex, the quadratic function in vertex form corresponding to this parabola is given by 

f(x) = a (x - h)^ 2 + k 

(h,k) = (0,-2)  coordinates of vertex

f(x) = a ( x - 0)^2 + (-2)

y = a(x^2) - 2

(2,0) is a point on the parabola

0 = a(2^2) -2
2 = 4a
a = 2/4 = 1/2

Equation:  y = 1/2 (x^2) - 2

directrix · Answer

Click on link to see graph: http://www.wolframalpha.com/input/?i=y+%3D+1%2F2+%28x%5E2%29+-2+

directrix · Answer

OK?

anonymous · Answer

thanks! ^_^

directrix · Answer

Any time - thanks for the medal. :)