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Find the value of k so that the function f is continuous at the indicated point. f(x) = {๐‘˜โข๐‘ฅ + 1, if ๐‘ฅ โ‰ค 5, 3โข๐‘ฅ โˆ’ 5, if ๐‘ฅ > 5 at x = 5

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Question

Find the value of k so that the function f is continuous at the indicated point.

f(x) = `{(kx + 1", if"  x <= 5),(3x - 5", if"  x > 5):}` at x = 5

Sum
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Solution

f(x) = `{(kx + 1", if"  x <= 5),(3x - 5", if"  x > 5):}`

If f(x) is continuous at x = 5, this implies:

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

⇒ k(5) + 1 = 3(5) − 5

⇒ 5k + 1 = 15 − 5

⇒ 5k + 1 = 10

⇒ 5k = 10 − 1

⇒ 5k = 9

⇒ k = `9/5`

That is, for the quantity k = `9/5` this function is continuous at x = 5.

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Chapter 5: Continuity and Differentiability - Exercise 5.1 [Page 161]

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NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 5 Continuity and Differentiability
Exercise 5.1 | Q 29 | Page 161

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