Question 331593
You should compare it to the equation for a parabola:


y = a(x-p)^2 + q.


You know that (p,q) is the vertex, and a determines the 'steepness' and direction of the parabola.


For your equation, a=-1/3, which means it opens down, and it is wider, and less steep, than the normal y=x^2 graph. It's a negative number, so it means that the parabola opens down.


Your vertex will be found at (2,1). This means that the axis of symmetry is x=2.


The easiest way to construct the graph (if you don't have a graphing calculator) is to make a table of values.


Try this site to get an image of what it should look like, and try to make your graph look like it.


http://www.wolframalpha.com/input/?i=y+%3D+-1/3(x-2)^2+%2B+1