The formula for the discriminant is b^2-4ac. The formula you wote is in the form of
ax^2+c=0, so first, you need to bring that -2 to the left. When you do that, you get (the original equation would be ax^2+bx+c but you have no bx.)
3x^2-8
So, since there's no b, it would be
b^2-4ac
0^2-4(3)(-8
-12 x -8
96
