Question 923858
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
............
Finding Vertex Form by Completing the Square

y= 3x^2-30x+18 
y = 3(x-5)^2 - 75 + 18
y = 3(x-5)^2 -57
V(5, - 57)
{{{drawing(300,300,   -50,50,-60,50, blue(line(5,50,5,-60))  ,  
 grid(1),
circle(5, -57,1.0),
graph( 300, 300, -50,50,-60,50,0, 3x^2-30x+18 ))}}}