Question 186591
Standard vertex form:
y= a(x-h)^2+k 
where
(h,k) is the vertex
.
y=-3x^2+6x
y=-3(x^2-2x)
At this point, you "complete the square"
y=-3(x^2-2x+1) + 3
y=-3(x^2-1)^2 + 3
.
By inspection...
Therefore, the vertex is at (1,3)