Please help on Algebra 2 inverse functions problem?

i don't understand square roots i dont want answers i just need help figuring it out how to solve inverse functions: f(x)= √ x-4, g(x)=x^2+4 x≥0 f(x)=½x³, g(x)=³2x f(x)=x², x≥0, g(x)=4^3x-6 f(x)=(3/4)x^4+2, g(x)=4^√(108x-216/3)