Okay, here we have this;
Considering the provided parabola, we are going to calculate the requested vertex and two points on each side of the vertex to later graph it, then we have:
Vertex:
Recall that in an equation of the form: y=a(x−h)^2+k. the vertex of the parabola is the point (h,k).
So according to that, in this case for our function we have:
y=a(x−h)^2+k
y= -3(x-0)^2+3
Then, the vertex of the function is (0,3)
Now we will calculate two points to the left taking x=-1 and x=-2, and two to the right taking x=1, x=2.
x=-1:
y= -3x^2+3
y= -3(-1)^2+3
y= -3(1)+3
y= -3+3
y=0
x=-2:
y= -3x^2+3
y= -3(-2)^2+3
y= -3(4)+3
y= -12+3
y=-9
x=1:
y= -3x^2+3
y= -3(1)^2+3
y= -3(1)+3
y= -3+3
y=0
x=2:
y= -3x^2+3
y= -3(2)^2+3
y= -3(4)+3
y= -12+3
y=-9
Now plotting the points we have: