Question:
Show that the function $f: R \rightarrow R: f(x)=x^{2}$ is neither one-one nor onto.
Solution:
To prove: function is neither one-one nor onto
Given: $f: R \rightarrow R: f(x)=x^{2}$
Solution: We have,
$f(x)=x^{2}$
For, $f\left(x_{1}\right)=f\left(x_{2}\right)$
$\Rightarrow \mathrm{x}_{1}^{2}=\mathrm{x}_{2}^{2}$
$\Rightarrow \mathrm{x}_{1}=\mathrm{x}_{2}$ or, $\mathrm{x}_{1}=-\mathrm{x}_{2}$
Since $x_{1}$ doesn't has unique image
$\therefore f(x)$ is not one-one
$f(x)=x^{2}$
Let $f(x)=y$ such that $y \in R$
$\Rightarrow y=x^{2}$
$\Rightarrow x=\sqrt{y}$
If $y=-1$, as $y \in R$
Then $x$ will be undefined as we cannot place the negative value under the square root Hence $f(x)$ is not onto
Hence Proved