Can someone show me how to do this... Find a value o c that satisfies the conlusion of the Integral Mean Value Theorem.

3X^2(=8) on [0,2]

I know the answer is 2/squareroot(3), and it is solved by the quadratic formula, but do not know how to get that.

I also know that f(C)=4 OR 3C^2 = 4.