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Math Help - derivative problem

  1. #1
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    derivative problem

    Y(u)=(u^-2+u^-3)(u^5-2u^2), y'=?

    My attempt:

    =(-2u^-3 + -3u^-4)(u^5 - 2u^2) + (5u^4-4u)(u^-2+u^-3)
    =(-2u^2-4u^-1 -3u + 6u^-2) + (5u^2 +5u-4u^-1-4u^-2)
    =3u^2 +2u -8u^-1+2u^-2

    Where did it go wrong?

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  2. #2
    MHF Contributor Calculus26's Avatar
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    =(-2u^-3 + -3u^-4)(u^5 - 2u^2) + (5u^4-4u)(u^-2+u^-3)



    =(-2u^2 + 4u^-1 -3u + 6u^-2) + (5u^2 +5u-4u^-1-4u^-2)


    the u^-1 terms cancel
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  3. #3
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    ****EDIT: Damn, you beat me to it

    Quote Originally Posted by hazecraze View Post
    Y(u)=(u^-2+u^-3)(u^5-2u^2), y'=?

    My attempt:

    =(-2u^-3 + -3u^-4)(u^5 - 2u^2) + (5u^4-4u)(u^-2+u^-3)
    =(-2u^2+4u^-1 -3u + 6u^-2) + (5u^2 +5u-4u^-1-4u^-2)
    =3u^2 +2u -8u^-1+2u^-2

    Where did it go wrong?
    Try multiplying the brackets together before you take the derivative.
    It will be much easier.
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