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Math Help - [SOLVED] Help me find this differential

  1. #1
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    Exclamation [SOLVED] Help me find this differential

    This is the question-

    part a) let g(x,y)= root (x^2-y^2)

    find the differential dg of g

    [ my answer is dg= x(dx)/root(x^2-y^2) - y(dy)/root(x^2-y^2)

    where dx is the small change and dy is a small change too..

    now part b) find an approx for root (13.4^2-11.7^2)

    i took x= 13 and y = 11 and my dx=.4 and dy=.7

    when i use my part a and sub them in i should get somewhere near 6.5 which i dont

    HELP ME PLEASE
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  2. #2
    MHF Contributor Calculus26's Avatar
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    df = -.361

    don't forget this is the change in f

    to get your approx add to f(13,11)

    sqrt(13^2 -11^2)= 6.928

    sqrt(13.4^2 -11.7^2) = 6.567
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  3. #3
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    ohh yes thanks change dam it i was doing it right then thanks
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