Question 817916
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
the vertex form of a Parabola opening up(a>0) or down(a<0), {{{y=a(x-h)^2 +k}}} 
where(h,k) is the vertex  and  x = h  is the Line of Symmetry
The standard form is {{{(x -h)^2 = 4p(y -k)}}}, where  the focus is (h,k + p)
A vertical parabola has a vertex at (-3,-2) 
 y = a(x+3)^2-2    |passes through the point (-1,7). 
 7 = a(2^2)-2
 9/4 = a
 {{{y = (9/4)(x+3)^2-2}}}
  {{{(4/9)(y+2) = ( x+3)^2 }}}  4p = 4/9,  p = 1/9   F(3, -17/9) 
{{{drawing(300,300,   -6, 6, -3, 3, grid(1), 
circle(-3, -2,0.2),
circle(-1, 7,0.2),
circle(-3, -17/9,0.2),
graph( 300, 300, -6, 6, -3, 3,0,-19/9, 2.14(x+3)^2-2))}}}