The domain of #g^(-1)(x)# is the range of #g(x)#, and the range of #g^-1(x)# is the domain of #g(x)#.
This is because #g^-1(x)# is a reflection of #g(x)# in the line #y=x#, so all the #x# coordinates switch to be the #y# coordinates, and the #y# coordinates become the #x# coordinates (e.g. if a point on #g(x)# is #(2,4)#, this would translate to #(4,2)# on #g^-1(x)#). Hence the range and domain would also switch around.