Question 117604
The vertex form of a parabola's equation is generally expressed as : 
{{{y= a(x-h)^2+k }}} where (h,k) is the vertex.


You are given the vertex (-2-2), so the equation becomes:


{{{y= a(x-(-2))^2+(-2)}}}
{{{y=a(x+2)^2-2}}}


Since the parabola contains the point (1, -20), substitute these values for x and y, and then solve the equation for a:


{{{-20=a(1+2)^2-2}}}
{{{-9a=20-2}}}
{{{a=-(18/9)=-2}}}


Now replace a with the value determined,
{{{y=-2(x+2)^2-2}}}