If f:N→N,f is a one-one function such thatf(g(x))=f(x)rg(x)=x, which is not the caseIf ff:N→Nf is an onto function such that f(g(x))=f(x), one possibility is f(x)=[
n
x=3n+1
n
x=3n+2
n
x=3n+3
n∈N0. Here f(x) is onto, also f(g(x))=f(x)‌∀x∈N