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Math Help - differentials...

  1. #1
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    differentials...

    question : find and evaluate and compare DELTAy and dy
    ----------------------------------------------------------
    given data:
    y = x^(4)+1 x = -1 DELTAx=dx=.01



    to obtain deltaY i use this equation
    DELTAy = (fx+DELTAx)-f(x)
    -----------------------------------------------
    which when i plug in the above data i get....
    DELTAy = -.99-0
    DELTAy = -.99
    ----------------------------------------------------
    the back of my book says DELTAy should be... -0.039
    what am i doing wrong :/
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  2. #2
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    Quote Originally Posted by nuclear123 View Post
    question : find and evaluate and compare DELTAy and dy
    ----------------------------------------------------------
    given data:
    y = x^(4)+1 x = -1 DELTAx=dx=.01



    to obtain deltaY i use this equation
    DELTAy = (fx+DELTAx)-f(x)
    -----------------------------------------------
    which when i plug in the above data i get....
    DELTAy = -.99-0
    DELTAy = -.99
    ----------------------------------------------------
    the back of my book says DELTAy should be... -0.039
    what am i doing wrong :/
    \Delta y = f(x+\Delta x)-f(x)

    =((-.99)^4+1)-((1)^4+1)

    dy = f'(x)\,dx

    =4x^3\,dx

    =4(-1)^3(.01)
    Last edited by ione; March 28th 2010 at 07:08 PM.
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