y = 1/3 x^2
The vertex of this parabola = (0, 0), because it does not have values of x1 and y1.
I'll choose 4 points of this parabola
x y
-5 y = 1/3 (-5)^2 = 25/3
-2 y = 1/3(-2)^2 = 4/3
0 y = 1/3(0)^2 = 0
2 y = 1/3(2)^2 = 4/3
5 y = 1/3(5)^2 = 25/3
Graph