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Discuss the continuity of the following function at the point(s) or on the interval indicated against them: f(x) =x3-3x-10x-5,for 3≤x≤6, x≠5=10,for x=5=x2-3x-10x-5,for 6<x≤9

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Question

Discuss the continuity of the following function at the point(s) or on the interval indicated against them:

f(x) `{:(= (x^2 - 3x - 10)/(x - 5)",", "for"  3 ≤ x ≤ 6","  x ≠ 5),(= 10",", "for"  x = 5),(=(x^2 - 3x - 10)/(x - 5)",", "for"  6 < x ≤ 9):}`

Sum
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Solution

`(x^2 - 3x - 10)/(x - 5)` is not defined at x = 5

∴ f(x) = `(x^2 - 3x - 10)/(x - 5)` where x ∈ [3, 5) ∪ (5, 6]

We can write f(x) explicitly, as follows:

f(x) `{:(=(x^2 - 3x - 10)/(x - 5),","  3 ≤ x < 5),(= 10, ","  x = 5),(= (x^2 - 3x - 10)/(x - 5), ","  5 < x ≤ 6),(= (x^2 - 3x - 10)/(x - 5), ","  6 < x ≤ 9):}`

∵ x2 – 3x – 10 = (x – 5) (x + 2)

∴ f(x) `{:(= x + 2",", 3 < x < 5),(= 10",", x = 5),(= x + 2",", 5 < x):}`

f(5) = 10

`lim_(x -> 5^-) "f"(x) = lim_(x -> 5^-) (x + 2)` = 5 + 2 = 7

`lim_(x -> 5^+) "f"(x) = lim_(x -> 5^+) (x + 2)` = 5 + 2 = 7

∴ f(5) = `lim_(x -> 5) "f"(x)`

∴ f(x) is continuous on its domain except at x = 5

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Chapter 8: Continuity - MISCELLANEOUS EXERCISE-8 [Page 177]

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