Question 254282
given
vertex (2, -3)
contains points (-1,-12)
y-k=a(x-h)squared
she has to find "a"
then plug in to the vertex form to find the ax form
.
The "vertex form" of a parabola is:
y= a(x-h)^2+k 
http://www.mathwarehouse.com/geometry/parabola/standard-and-vertex-form.php
.
y-k = a(x-h)^2
where
(h,k) is the vertex
.
Plug in what the problem gave:
vertex (2, -3)
contains points (-1,-12)
y-k = a(x-h)^2
Plugging in (2, -3) we get:
y-(-3) = a(x-2)^2
Plugging in our point (-1,-12)
-12-(-3) = a(-1-2)^2
-12+3 = a(-3)^2
-9 = a(9)
-1 = a