You are given the vertex first so then you plug in the vertex in the vertex form for a quadratic equation which is y=a(x-h)^2+k. After you plug it in, you should have the equation y=a(x+2)^2-20. You are also given another point (0,-12) You then plug in the coordinates and solve for a. After you find your a you simply input the a,h and k values and leave the x and y alone.