Prove that the function f : N N : f(n) = (n2 + n + 1) is one - one but not onto.

In the given range of N f(x) is monotonically increasing.


f(n) = n2 + n + 1 is one one.



But Range of f(n) = [0.75,∞)≠N(codomain)


Hence,f(n) is not onto.


Hence, proved that the function f : N N : f(n) = (n2 + n + 1) is one - one but not onto.


1