Question 919447
the vertex form of a Parabola opening up(a>0) or down(a<0), {{{y=a(x-h)^2 +k}}}
the vertex form of a Parabola opening up(a>0) or down(a<0), 
{{{y=a(x-h)^2 +k}}}. V(h, k)
 Completing the Square to Obtain the Vertex Form:
y = ax^2 + bx + c = 0
f(x)=-3x^2+12x-9 = 0  {{{b/(-2a) = (12)/(6) = 2}}} 2 the x-value for the Vertex
y = -3(x - 2)^2 + 12 -9 = 0  {{{-a(b/(-2a))^2 }}}= 12
y = -3x - 2)^2 +3= 0   
y = -3(x - 2)^2 + 3 = 0
V(2,3)

{{{drawing(300,300,   -6, 6, -6, 6, grid(1), blue(line(2,6,2,-6)) ,
circle(2, 3,0.2),
graph( 300, 300, -6, 6, -6, 6,0, -3x^2+12x-9 ) )}}}