Question

i dont understand the 5th nad 6th step

please explain fastt

ive got an exam

sales pe frieght outward lagta h ya inward give me example

Let  f :{1,2,3}-> {a,b,c} be one –one and onto function given by f(1)=a.f(2)=b and f(3)=c. show that there exists a function g:{a,b,c}->{1,2,3} such that go f= and fog =,where X={1,2,3} and Y={a,b,c}.

Can we use the first 3 observations instead of using binomial theorem?!

 Under which head this accumulated depreciation will be created