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Discuss the Continuity of the Function (X) = (3 - Sqrt(2x + 7))/(X - 1) for X ≠ 1 = -1/3 For X = 1, at X = 1 - Mathematics and Statistics

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Question

Discuss the continuity of the function `f(x) = (3 - sqrt(2x + 7))/(x - 1)` for x ≠ 1

= `-1/3`   for x = 1, at x = 1

Sum

Solution

Given `f(1) = (-1)/3`
Consider 

`lim_(x ->1) f(x) = lim_(x ->1) (3 - sqrt(2x + 7))/(x - 1)`

                   = `lim_(x ->1) (3 - sqrt(2x + 7))/(x - 1) xx (3 + sqrt(2x + 7))/(3 + sqrt(2x + 7))`

                  = `lim_(x ->1) (9 - 2x - 7)/((x - 1) (3 + sqrt(2x + 7))`

                 = `lim_(x ->1) (2 - 2x)/((x - 1) (3 + sqrt(2x + 7))`

                 = `lim_(x ->1) (-2(x - 1))/((x - 1) (3 + sqrt(2x + 7))`

                = `lim_(x ->1) (-2)/(3 + sqrt(2x + 7)`

                                                                (`therefore x -> 1, ( x- 1) ≠ 0)`

               = `(-2)/(3 + sqrt(2x + 7)`

               = `(-2)/(3 + sqrt9)`

               = `(-2)/(3 + 3)`

               = `(-2)/6`

               = `(-1)/3`

`lim_(x ->1) f(x) = f(1)`

Function is continuous at x = 1

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2013-2014 (October)

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