Pre-Algebra/Graphing Quadratic Equations

I dont exactly understand how I would solve these, our teacher says we MUST use a DATA TABLE to solve. The one I am currently stuck on is this:
y= 1/2x^2
my data table looks like this
X Y
-4
-3
-2
-1
0
1
2
3
4
How do I figure out the y's ?