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Tamil Nadu Board of Secondary EducationHSC Science Class 11

Find the points of discontinuity of the function f, where ,if,iff(x)={4x+5, if x≤34x-5, if x>3 - Mathematics

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Question

Find the points of discontinuity of the function f, where `f(x) = {{:(4x + 5",",  "if",  x ≤ 3),(4x - 5",",  "if",  x > 3):}`

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Solution

`lim_(x -> 3) f(x) =  lim_(x -> 3^-) (4x + 5)`

= 4 × 3 + 5

`lim_(x -> 3) f(x)` = 17   .........(1)

`lim_(x -> 3) f(x) =  lim_(x -> 3^+) (4x - 5)`

= 4 × 3 – 5

`lim_(x -> 3) f(x)` = 12 – 5 = 7   .........(2)

From equations (1) and (2) we have

`lim_(x -> 3) f(x) ≠  lim_(x -> 3^+) f(x)`

∴ `lim_(x -> 3) f(x)` does not exist.

Hence f(x) is not continuous at x = 3.

∴ x = 3 is the point of dicontinuity.   

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Chapter 9: Differential Calculus - Limits and Continuity - Exercise 9.5 [Page 127]

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Samacheer Kalvi Mathematics - Volume 1 and 2 [English] Class 11 TN Board
Chapter 9 Differential Calculus - Limits and Continuity
Exercise 9.5 | Q 3. (i) | Page 127

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