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Homework Help: How is this question solved?

  1. Jun 12, 2010 #1
    [PLAIN]http://img517.imageshack.us/img517/6328/q75c.gif [Broken]

    I know that you have to substitute u=2x+1 into the second equation, but I don't know where to go from there.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jun 12, 2010 #2
    Let [tex] \int f(x) dx = F(x) [/tex]

    then [tex] \int ^3_{-1} f(x) dx = F(3) - F(-1) = 12[/tex]

    so [tex] \int^1_{-1} f(2x+1) dx = ? [/tex]
  4. Jun 12, 2010 #3
    The answer given is 6, whereas that gives me 12.
  5. Jun 12, 2010 #4


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    Science Advisor
    Homework Helper

    Try actually doing the substitution. If u=2x+1, what's the relation between dx and du?
  6. Jun 12, 2010 #5
    Oh, I get it now.
  7. Jun 13, 2010 #6


    Staff: Mentor

    So now you'll need to change your user name.:biggrin:
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