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NCERT Class XI Mathematics - Limits and Derivatives - Solutions

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Question : 25 of 72
Marks: +1, -0
Evaluate lim⁡x→0\lim\limits_{x\rightarrow0} f (x), where f (x) = {∣x∣x,x≠00,x=0\begin{cases} \frac{|x|}{x}, & x \neq 0 \\ 0, & x = 0 \end{cases}
Solution:  
We have, f (x) = {∣x∣x,x≠00,x=0\begin{cases} \frac{|x|}{x}, & x \neq 0 \\ 0, & x = 0 \end{cases}
Now , lim⁡x→0−\lim\limits_{x\rightarrow0^{-}} f (x) = lim⁡x→0−\lim\limits_{x\rightarrow0^{-}} ∣x∣x\frac{|x|}{x} = lim⁡x→0−\lim\limits_{x\rightarrow0^{-}} (−xx)\left(-\frac{x}{x}\right) [Since |x| = - x for x < 0]
= lim⁡x→0−\lim\limits_{x\rightarrow0^{-}} (- 1) = - 1
and lim⁡x→0+\lim\limits_{x\rightarrow0^{+}} f (x) = lim⁡x→0+\lim\limits_{x\rightarrow0^{+}} ∣x∣x\frac{|x|}{x} = lim⁡x→0+\lim\limits_{x\rightarrow0^{+}} (xx)\left(\frac{x}{x}\right) [Since |x| = x , for x > 0]
= lim⁡x→0+\lim\limits_{x\rightarrow0^{+}} (1) = 1
Since lim⁡x→0−\lim\limits_{x\rightarrow0^{-}} f (x) ≠ lim⁡x→0+\lim\limits_{x\rightarrow0^{+}} f (x)
Thus lim⁡x→0\lim\limits_{x\rightarrow0} f (x) does not exist.
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