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Math Help - simple quotient rule

  1. #1
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    simple quotient rule

    how does the derivative of

    -1/ (x - 1)^2

    =

    2/ (x - 1)^3

    seems simple..but i get x in the numerator
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  2. #2
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    \frac{-1}{(x-1)^2}=-(x-1)^{-2}


    It should be easy now
    Right?
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  3. #3
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    thank you but do you know how do do it with quotient rule? my teacher emphasizes this.
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  4. #4
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by calculus0 View Post
    thank you but do you know how do do it with quotient rule? my teacher emphasizes this.
    u = -1 \: \rightarrow \: u' = 0

    v = (x-1)^2 \: \rightarrow \: v' = 2(x-1)

    Quotient Rule y' = \frac{u'v - v'u}{v^2}

    In this case we can get rid of u'v because it equals 0.

    y' = -\frac{v'u}{v^2}. Remember your signs and factors
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  5. #5
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    im so horrible at this..

    after 1/2 the equation disappears multiplying by zero i get:

    2
    -----------
    (x - 1)

    which is not equal to the solution

    2
    ------------
    (x - 1)^3
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  6. #6
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by calculus0 View Post
    im so horrible at this..

    after 1/2 the equation disappears multiplying by zero i get:

    2
    -----------
    (x - 1)

    which is not equal to the solution

    2
    ------------
    (x - 1)^3
    The problem seems to be that you're putting v on the denominator instead of v^2:

    v^2 = (x-1)^4


    which gives y' = \frac{2(x-1)}{(x-1)(x-1)^3}

    I have put in that form to make it easier to see what cancels out
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  7. #7
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    think i got it...e^(i*pi)

    thanks so much
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