What is (f. g)(x)?

f(x)=x^3 - 4x + 2
g(x)=x^2 + 2

To find the inverse of a number a, one can use the equation f(c) = a-1/c=0 where c is the inverse of a use the secant method of finding roots of equations to find the inverse of a = 2.5 ,er = 0.001%