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Q. The range of the function $f \left(x\right)=\frac{x}{1+\left|x\right|}, x\,\in\,R,$ is

AIEEEAIEEE 2012Relations and Functions

Solution:

Domain: Let $f : A \rightarrow B$ be a function, then the set $A$ is called as the domain of the function $f$.
Co-domain:
Let $f : A \rightarrow B$ be a function, then the set $B$ is called as the co-domain of the function $f$.
Range: Let $f : A \rightarrow B$, then the range of the function $f$ consists of those elements in $B$ which have at least one pre - image in $A$. It is denoted as $f(A)$.
i.e $f(A)=\{b \in B \mid f(a)=b$ for some $a \in A\}$ Note: Range is the subset of codomain of $f$.
Calculation: Given: $f(x)=\frac{|x|}{x}, x \neq 0$ $ \Rightarrow f(x)=\frac{|x|}{x}=\left\{\begin{array}{c} \frac{x}{x}=1, x>0 \\ -\frac{x}{x}=-1, x<0 \end{array}\right. $
As we know that, if $f: A \rightarrow B$, then the range of the function $f$ consists of those elements in $B$ which have at least one pre - image in $A$. It is denoted as $f(A)$. Hence, the range of the given function is $\{1,-1\}$.