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Identify discontinuity for the following function as either a jump or a removable discontinuity on their respective domain: f(x) =x2+x+1x+1,for x∈[0,3)=3x+4x2-5,for x∈[3,6] - Mathematics and Statistics

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Question

Identify discontinuity for the following function as either a jump or a removable discontinuity on their respective domain:

f(x) `{:(= (x^2 + x + 1)/(x + 1)"," , "for"  x ∈ [0, 3)),(=(3x +4)/(x^2 - 5)"," , "for"  x ∈ [3, 6]):}`

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Solution

For x ∈ [0, 3), f(x) = `(x^2 + x + 1)/(x + 1)`, being a rational function is continuous except when its denominator x + 1 = 0 i.e., at x = – 1, which does not belong to [0, 3)

∴ f is continuous on [0, 3).

For x ∈ [3, 6], f(x) = `(3x + 4)/(x^2 - 5)`, being a rational function is continuous except when its denominator x2 – 5 = 0 i.e., at x = `±  sqrt(5)` But `±  sqrt(5) ∉ [3,  6]`

∴ f is continuous on [0, 6] except possibly at x = 3

Continuity at x = 3

f(x) = `(x^2 + x + 1)/(x + 1)`, for x ∈ [0, 3)

∴ `lim_(x -> 3^-) "f"(x) =  lim_(x -> 3) (x^2 + x + 1)/(x + 1)`

= `(lim_(x -> 3)(x^2 + x + 1))/(lim_(x -> 3) (x + 1))`

= `(9 + 3 + 1)/(3 + 1)`

= `13/4`

Also, f(x) = `(3x + 4)/(x^2 - 5)`, for x ∈ [3, 6]

∴ `lim_(x -> 3^+) "f"(x) = "f"(3) = (9 + 4)/(9 - 5) = 13/4`

∴ `"f"(3) = lim_(x -> 3^+) "f"(x) = lim_(x -> 3^-) "f"(x)`

∴ f is continuous at x = 3.

Hence, f is continuous on its domain [0, 6].

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Continuous and Discontinuous Functions
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Chapter 8: Continuity - MISCELLANEOUS EXERCISE-8 [Page 177]

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