Tentang invers fungsi.. Tolong dijawab ya

misal f(x)=y
a.y=4x-3
4x=y+3
x=y+3 /4
f^-1(y)=y+3 /4
f^-1(x)=x+3 /4
b.y=2x^2
x^2=y/2
x=akar y/2
=akar 1/4.2y
=1/2 akar 2y
f^-1(x)=1/2 akar 2x