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Homework Help: Sketch the region enclosed by y= 6|x| and y = x^2 -7

  1. Dec 8, 2009 #1
    i know that the way to solve this is by evaluating the integral from a to b of the first function minus the second one but how would i solve for x to find out what the limits of integration should be?

    if you set them equal to each other you get 6|x| = x^2 - 7
    but im not exactly sure what to do with the |x|
  2. jcsd
  3. Dec 8, 2009 #2
  4. Dec 8, 2009 #3
    like rootX said, when dealing with absolute value functions, it's usually best to define it peace-wise.

    f(x) = 6x for x >= 0
    -6x for x < 0

    Or you could notice that the two functions are even, and you could thus solve for x using 6x, and keep in mind that there is another intersection point opposite the y-axis.
  5. Dec 8, 2009 #4


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    If [itex]x\ge 0[/itex], |x|= x so this is 6x= x^2- 7 which is the same as x^2- 6x- 7= 0.

    If x< 0, |x|= -x so this is -6x= x^2- 7 which is the same as x^2+ 6x- 7= 0.
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