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NCERT Class XI Mathematics - Limits and Derivatives - Solutions

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Question : 27 of 72
Marks: +1, -0
Find lim⁡x→5\lim\limits_{x\to 5} f (x) , where f (x) = |x| - 5
Solution:  
We have, f (x) = |x| - 5
Now, lim⁡x→5−\lim\limits_{x\to 5^{-}} f (x) = lim⁡x→5−\lim\limits_{x\to 5^{-}} (|x| - 5) = lim⁡x→5−\lim\limits_{x\to 5^{-}} (x - 5) [Since |x| = x , for x > 0]
= 5 - 5 = 0
and lim⁡x→5+\lim\limits_{x\to 5^{+}} f (x) = lim⁡x→5+\lim\limits_{x\to 5^{+}} (|x| - 5)
lim⁡x→5+\lim\limits_{x\to 5^{+}} (x - 5) = 5 - 5 = 0 [Since |x| = x, for x > 0]
∴ lim⁡x→5−\lim\limits_{x\to 5^{-}} f (x) = lim⁡x→5+\lim\limits_{x\to 5^{+}} f (x)
Thus lim⁡x→5\lim\limits_{x\to 5} f (x) = 0.
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