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Continuity on piecewise function

  1. Jul 1, 2011 #1
    1. The problem statement, all variables and given/known data
    [10 Marks] At which points is the following function continuous and at which point is it discontinuous. Explain the types of discontinuity at each point where the function is discontinuous. Then at each point of the discontinuity, if possible, find a value for f(x) that makes it continuous or one sided continuous.

    f(x) =
    -2x if -1[itex]\leq[/itex]x<1
    -2/(x-1) if 1<x<2
    x-2 if x> 2
    2. Relevant equations

    Test continuity at point:
    f(a) is defined
    lim f(x) exists
    lim f(x) = f(a)

    Continuity at Endpoints
    lim f(x) = f(a) = left continuous
    lim f(x) = f(a) = right continuous

    3. The attempt at a solution

    Im thinking what I need to do, is:
    Check for continuity at the points -1, 1, 2.
    Then I would classify any discontinuities as either removable, jump, or infinite discontinuities.
    But that last part, im not sure what its asking?
    What I have is this so far:

    Discontinuous at x=1 and x=2.
    At x=1: Jump discontinuity
    At x=2: Jump discontinuity

    Im not sure if im supposed to do this or if its right, but I did it anyway:
    At x=-1, the function is right continuous on the interval [-1, 1). The function is also continuous on (1, 2) and (2, infinity)
  2. jcsd
  3. Jul 1, 2011 #2


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    Science Advisor

    Basically correct but the discontinuity at x= 1 is NOT a "jump" discontinuity:
    [tex]\lim_{x\to 1^+} f(x)= \lim_{x\to 1}\frac{-2}{x- 1}= -\infty[/tex]
  4. Jul 1, 2011 #3
    Oh really? Cool! Thanks! So by stating the intervals of continuity, I satisfied the last part of the problem? Cause I was not sure what it was asking..
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