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Find limx→1 f(x), where f(x)={x2-1x≤1-x2-1x>1

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Question

Find `lim_(x -> 1)` f(x), where `f(x) = {(x^2 -1, x <= 1), (-x^2 -1, x > 1):}`

Sum
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Solution

When x < 1, f(x) = x2 − 1

By keeping the value of x in the function less than 1 and near 1,

x 0.9 0.99 0.999
f(x) −0.19 −0.0199 −0.0019999

∴ `lim_("x" → 1^-) f("x") = 0`

When x >1, f(x) = −x2 − 1      ....(i)

If the value of x in the function is kept greater than 1 and close to 1,

x 1.1 1.01 1.0001
f(x) −2.21 −2.0201 −2.002001

∴ `lim_("x" → 1^+) f("x") = -2`    .....(ii)

From equations (i) and (ii),

`lim_("x" → 1^-) f("x") ≠ lim_("x" → 1^+) f("x")`

∴ Hence, the equation does not exist at x = 1.

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Chapter 12: Limits and Derivatives - EXERCISE 12.1 [Page 238]

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NCERT Mathematics [English] Class 11
Chapter 12 Limits and Derivatives
EXERCISE 12.1 | Q 24. | Page 238

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