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Math Help - derivative question

  1. #1
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    derivative question

    Hi this should be easy but im having a bit of a brain block.

    find the derivative of this with respect to x

    -(x+1)(ln(y*z*r)
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    Quote Originally Posted by stumped765 View Post
    Hi this should be easy but im having a bit of a brain block.

    find the derivative of this with respect to x

    -(x+1)(ln(y*z*r)
    Are y, z and r constants or are any of them functions of x?
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  3. #3
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    they can be regarded as constants
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    Quote Originally Posted by stumped765 View Post
    Hi this should be easy but im having a bit of a brain block.

    find the derivative of this with respect to x

    -(x+1)(ln(y*z*r)
    If y, z, r are constants, then \ln{(yzr)} is also a constant.

    So \frac{d}{dx}\left[-(x + 1)\ln{(yzr)}\right] = -\ln{(yzr)}.
    Last edited by Prove It; January 20th 2010 at 09:25 PM.
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    Quote Originally Posted by Prove It View Post
    If y, z, r are constants, then \ln{(yzr)} is also a constant.

    So \frac{d}{dx}\left[-(x + 1)\ln{(yzr)}\right] = -x\ln{(yzr)}.
    Typo- that 'x' should not be in the final answer. This is simply -x C+ C (where I have written the constant ln(yzr) as "C"), linear in x, so its derivative is the constant -C= -ln(xzr).
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    Quote Originally Posted by HallsofIvy View Post
    Typo- that 'x' should not be in the final answer. This is simply -x C+ C (where I have written the constant ln(yzr) as "C"), linear in x, so its derivative is the constant -C= -ln(xzr).
    Yes, typo. Thanks.
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