You can simply substitute the equations into f(g(x)).
First, substitute the equivalent expression for g(x). You are given g(x) = 2x^2.
f(g(x)) = f(2x^2)
2x^2 is now the new "x" in the given equation f(x) = 4x + 2. Replace the x's in f(x) = 4x + 2 with 2x^2.
f(x) = 4x + 2
f(2x^2) = 4(2x^2) + 2
Finally simplify the expression.
4(2x^2) + 2 = 8x^2 + 2
