Question:

What is the derivative of ln(x+1/x)?

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What is the derivative of ln(x+1/x)?

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  1. f(x) = ln(x+1) - ln(x)

    Now take derivative

    f'(x) = 1/(x+1) - 1/x


  2. d/dx ln(x+1/x)

    let u = x+1/x and use the chain rule

    d/du ln(u) du/dx

    d/du ln(u) = 1/u

    d/dx(x + 1/x) = d/dx(x) + d/dx(1/x) = 1 - 1/x²

    (1 - 1/x²)/(x+1/x) = [(x²-1)/x²] / [(x²+1)/x] = (x²-1)/(x³+x)

    Answer: (x²-1)/(x³+x)

  3. ln(x+1/x)=ln((x^2+1)/x)=ln(x^2+1)-ln(x).... x^2+1=u..

    so du/dx=2x..if f(x)=ln(u)-ln(x)...so f'(x)=(1/u)du/dx-1/x....putting back the u, we have f'(x)=(1/(x^2+1))2x-1/x=2x/(x^2+1)-1/x=(...

    u original question is misleading...according to the general rule, u should multiply, divide and add before substract unless u put a bracket before x+1.....

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