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Find the values of a and b such that the function defined by ,,,f(x)={5,ifx≤2ax+b,if2<x<1021,ifx≥10 is a continuous function. - Mathematics

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प्रश्न

Find the values of a and b such that the function defined by `f(x) = {(5, "," if x <= 2),(ax +b, "," if 2 < x < 10),(21, "," if x >= 10):}`  is a continuous function.

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उत्तर

`f(x) = {(5, "," if x <= 2),(ax +b, "," if 2 < x < 10),(21, "," if x >= 10):}` 

Since f(x) = 5, f(x) = ax + b, f(x) is a continuous function at 21 times, f(x) is already a continuous function at x < 2, 2 < x < 10, x > 10.

If f(x) is continuous at x = 2, this implies:

`f(2) = lim_(x -> 2^+) f(x) = lim_(x -> 2^-) f(x)`

`=> 5 = a(2) + b  = 5`

`=> 2a + b  = 5`         ...(1)

If f(x) is continuous at x = 10, this implies:

`f(10) = lim_(x -> 10^+)  f(x) = lim_(x -> 10^-)  f(x)`

`=> 21 = 21 = a(10) + b `

`=> 10a + b  = 21`       ...(2)

Subtracting equation (2) from (1),

`=> 8a = 16`

`=> a = 2`

`therefore (2) (2) + b  = 5`

`=> b = 1`

That is, the function f(x) is continuous for the quantities a = 2, b = 1.

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अध्याय 5: Continuity and Differentiability - Exercise 5.1 [पृष्ठ १६१]

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एनसीईआरटी Mathematics [English] Class 12
अध्याय 5 Continuity and Differentiability
Exercise 5.1 | Q 30 | पृष्ठ १६१

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