Let f∘gf∘g denote function composition such that (f∘g)(x)=f(g(x))(f∘g)(x)=f(g(x)). Let f:A→Bf:A→B such that for all g:B→Ag:B→A and h:B→Ah:B→A we have f∘g=f∘h⇒g=hf∘g=f∘h⇒g=h. Which of the following must be true?
Ans: One-one.
My doubt: WHY IT IS NOT ONTO ?