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Math Help - how do i do this reverse integration

  1. #1
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    how do i do this reverse integration

    it is a double integeration

    integrate integrate dydx

    where my x and y value is

    1<x<0

    2<y<4-2x
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  2. #2
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    Quote Originally Posted by slurm View Post
    it is a double integeration

    integrate integrate dydx

    where my x and y value is

    1<x<0 Mr F says: Do you mean -1 < x < 0 ?

    2<y<4-2x
    First you draw the region defined by the inequalities. Have you done this?
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  3. #3
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    yes i done it but it seems i cant attach a picture to show my graph
    anyway after sketching

    i found out my range changes as it is now dxdy

    2<y<4

    0<x<[(y-4)/-2]
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  4. #4
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    it seems that is is not correct because integration of dxdy should be equal to dydx
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  5. #5
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    Quote Originally Posted by slurm View Post
    yes i done it but it seems i cant attach a picture to show my graph
    anyway after sketching

    i found out my range changes as it is now dxdy

    2<y<4

    0<x<[(y-4)/-2]
    You haven't answered my red question.
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  6. #6
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    oh no the range for x is 0 and 1, as if like 0 is lower boundary and 1 is upper boundary.. haha if only i could draw it in a text box it will be easier
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  7. #7
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    Quote Originally Posted by slurm View Post
    oh no the range for x is 0 and 1, as if like 0 is lower boundary and 1 is upper boundary.. haha if only i could draw it in a text box it will be easier
    Then it should be evident from your diagram that \int_{x = 0}^{x = 1} \int_{y = 2}^{y = 4 - 2x} dy \, dx =  \int_{y = 0}^{y = 4} \int_{x = 0}^{x = \frac{4 - y}{2}} dx \, dy.

    Also:

    Quote Originally Posted by slurm View Post
    it is a double integeration
    integrate integrate dydx

    where my x and y value is

    1<x<0 Mr F says: This should be 0 < x < 1.

    2<y<4-2x Mr F says: I hope the inequalities here are going the correct way.
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  8. #8
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    is this answer? but when i integrate the left side of ur ans i get 2 instead of 1
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  9. #9
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    oh no , a mistake in my integration.... sorry,got it already .thx alot
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  10. #10
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    yeah got it already, thanks alot another question i would like to ask since i be doing vector calculus

    i have a weakness in sketching and finding the limits of the integral. like for example sketching a parabola and such , do u have any tips in sketching graphs
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  11. #11
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    Quote Originally Posted by slurm View Post
    yeah got it already, thanks alor another question i would like to ask since i be doing vector calculus

    i have a weakness in sketching and finding the limits of the integral. like for example sketching a parabola and such , do u have any tips in sketching graphs
    Practice. Lots of it.
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  12. #12
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    yeah .. alright , i must agree that pressure really makes diamond, although i know nothing about chemistry, alright thanks alot again
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