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Homework Help: Double integral help

  1. Aug 10, 2011 #1
    ∫u=3 and l=0 u= x and l= 0∫ (x2 + y2 )dydx

    solve by reversing the order of integration. u and l means upper and lower limit. this is a double integral by the way. i dont understand how the limits are found when reversing the order and the idea of diagrams. please help me
  2. jcsd
  3. Aug 10, 2011 #2


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    I take it you need to do the following integration by reversing the order of integration.

    [tex]\int_0^3\int_0^x\,(x^2+y^2)\,dy\,dx [/tex]

    Sketch the region in the xy-plane.

    Then consider how you might cover the same region with the order reversed.
  4. Aug 10, 2011 #3
    can you please help me with it. i have been trying to do it since last week. how do u change the limits with the order. thats my question. can you please explain for this particular question?
  5. Aug 10, 2011 #4


    Staff: Mentor

    To repeat what SammyS said, sketch the region over which integration is being done. The limits of integration are x = 0 to x = 3, and y = 0 to y = x. What does this region in the plane look like?
  6. Aug 10, 2011 #5
    thanks alot..i got it :)
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