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Q. The domain and range of the real function $f$ defined by $f(x)=|x-1|$ is

Relations and Functions

Solution:

We have $f\left(x\right) =\left|x-1\right|$
Here, $f\left(x\right)$ is a modulus function and since modulus of a real number is uniquely defined $ \forall$ real positive number.
$\therefore $ The domain of $f\left(x\right)$ is $R$.
We see that $f\left(x\right) =\left|x-1\right|$
$f(x) = \begin{cases} x-1, & \text{if $x \ge\,1$} \\[2ex] -(x-1), & \text{if $x <\,1$ } \end{cases}$
$\Rightarrow $ $f(x) = \begin{cases} x-1, & \text{if $x \ge\,1$} \\[2ex] 1-x, & \text{if $x <\,1$ } \end{cases}$
From above, we observe that in both cases $f \left(x\right) \ge\, 0$.
Hence, range of $f(x)$ is $[0, \infty).$