Question

Is the function $f:N\to N$. (N is the set of natural numbers) defined by f(n)=2n+3 surjective ?

Answer 1

Given $f\left(n\right)=2n+3;n\in N$
Here, range of f is $\{5,7,\mathrm{9....}\}$
and co-domain is N.
Here, $Range\left(f\right)\ne co-domain$
Hence, f is not surjective.