Check the injectivity and surjectivity of the following function $f : N \rightarrow N$ given by $f(x) = x^{3}$.

Vedclass pdf generator app on play store
Vedclass iOS app on app store
(N/A) Given function is $f : N \rightarrow N$ defined by $f(x) = x^{3}$.
For injectivity:
Let $x, y \in N$ such that $f(x) = f(y)$.
Then $x^{3} = y^{3}$.
Since $x, y$ are natural numbers,taking the cube root on both sides gives $x = y$.
Therefore,$f$ is injective.
For surjectivity:
$A$ function is surjective if for every $y \in N$,there exists an $x \in N$ such that $f(x) = y$.
Consider $y = 2 \in N$.
We need $x^{3} = 2$,which implies $x = \sqrt[3]{2}$.
Since $\sqrt[3]{2}$ is not a natural number $(\sqrt[3]{2} \notin N)$,there is no $x \in N$ such that $f(x) = 2$.
Therefore,$f$ is not surjective.
Conclusion: The function $f$ is injective but not surjective.

Explore More

Similar Questions

Let $X$ be a set with exactly $5$ elements and $Y$ be a set with exactly $7$ elements. If $\alpha$ is the number of one-one functions from $X$ to $Y$ and $\beta$ is the number of onto functions from $Y$ to $X$,then the value of $\frac{1}{5!}(\beta-\alpha)$ is.

If a real-valued function $f:[a, \infty) \rightarrow [b, \infty)$ defined by $f(x) = 2x^2 - 3x + 5$ is a bijection,then $3a + 2b =$

Let $f: N \rightarrow N$ be defined by $f(n) = \begin{cases} \frac{n+1}{2}; & \text{if } n \text{ is odd} \\ \frac{n}{2}; & \text{if } n \text{ is even} \end{cases}$, for all $n \in N$ then $f$ is $\dots \dots \dots$

The function $f(x) = \log (x + \sqrt {{x^2} + 1} )$ is:

In each of the following cases,state whether the function is one-one,onto or bijective. Justify your answer. $f : R \rightarrow R$ defined by $f(x) = 3 - 4x$.

Vedclass Products

For Students

Vedclass Test Series

Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.

Start Free Trial
For Teachers

Exam Paper Generator

Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.

Try Free
For Institutes

Online Exam Module

Live online exams with unlimited students, 360° analytics & white-label branding.

See Demo