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F(x) = ,ifk,if{3x-8, if x≤52k, if x>5 at x = 5 - Mathematics

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Question

f(x) = `{{:(3x - 8",",  "if"  x ≤ 5),(2"k"",",  "if"  x > 5):}` at x = 5

Sum
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Solution

We have, f(x) = `{{:(3x - 8",",  "if"  x ≤ 5),(2"k"",",  "if"  x > 5):}` 

Since, f(x) is continuous at x = 5

∴ L.H.L. = R.H.L. = f(5)

Now, L.H.L. = `lim_(x -> 5^-) (3x - 8)`

= `lim_("h" -> 0) [3(5 - "h") - 8]`

= –15 – 8

= 7

R.H.L. = `lim_(x -> 5^+) 2"k"`

= `lim_("h" -> 0) 2"k"` = 2k

Also f(5) = 3(5) – 8 = 7

∴ 2k = 7

⇒ k = `7/2`

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Chapter 5: Continuity And Differentiability - Exercise [Page 108]

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NCERT Exemplar Mathematics [English] Class 12
Chapter 5 Continuity And Differentiability
Exercise | Q 11 | Page 108

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