Question

The function $f:N\to N$ ($N$ is the set of natural numbers) defined by $f\left(n\right)=2n+3$ is

• A. Surjective only
• B. Injective only
• C. Bijective
• D. neither one-one nor onto

Answer 1

The correct option is B Injective only

$f\left(n\right)=2n+3$ is a linear function.
Hence $f\left(n_1\right)=f\left(n_2\right)$$\Rightarrow n_1=n_2$
Here Domain is $N$ but range is set of all odd number $-\{1,3\}$
Hence $f\left(n\right)$ is injective or one-to-one function.