Mister Exam

Derivative of (x-2)(ln(x-1)-ln(x+1))

Function f() - derivative -N order at the point
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The solution

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(x - 2)*(log(x - 1) - log(x + 1))
(x2)(log(x1)log(x+1))\left(x - 2\right) \left(\log{\left(x - 1 \right)} - \log{\left(x + 1 \right)}\right)
(x - 2)*(log(x - 1) - log(x + 1))
Detail solution
  1. Apply the product rule:

    ddxf(x)g(x)=f(x)ddxg(x)+g(x)ddxf(x)\frac{d}{d x} f{\left(x \right)} g{\left(x \right)} = f{\left(x \right)} \frac{d}{d x} g{\left(x \right)} + g{\left(x \right)} \frac{d}{d x} f{\left(x \right)}

    f(x)=x2f{\left(x \right)} = x - 2; to find ddxf(x)\frac{d}{d x} f{\left(x \right)}:

    1. Differentiate x2x - 2 term by term:

      1. Apply the power rule: xx goes to 11

      2. The derivative of the constant 2-2 is zero.

      The result is: 11

    g(x)=log(x1)log(x+1)g{\left(x \right)} = \log{\left(x - 1 \right)} - \log{\left(x + 1 \right)}; to find ddxg(x)\frac{d}{d x} g{\left(x \right)}:

    1. Differentiate log(x1)log(x+1)\log{\left(x - 1 \right)} - \log{\left(x + 1 \right)} term by term:

      1. Let u=x1u = x - 1.

      2. The derivative of log(u)\log{\left(u \right)} is 1u\frac{1}{u}.

      3. Then, apply the chain rule. Multiply by ddx(x1)\frac{d}{d x} \left(x - 1\right):

        1. Differentiate x1x - 1 term by term:

          1. Apply the power rule: xx goes to 11

          2. The derivative of the constant 1-1 is zero.

          The result is: 11

        The result of the chain rule is:

        1x1\frac{1}{x - 1}

      4. The derivative of a constant times a function is the constant times the derivative of the function.

        1. Let u=x+1u = x + 1.

        2. The derivative of log(u)\log{\left(u \right)} is 1u\frac{1}{u}.

        3. Then, apply the chain rule. Multiply by ddx(x+1)\frac{d}{d x} \left(x + 1\right):

          1. Differentiate x+1x + 1 term by term:

            1. Apply the power rule: xx goes to 11

            2. The derivative of the constant 11 is zero.

            The result is: 11

          The result of the chain rule is:

          1x+1\frac{1}{x + 1}

        So, the result is: 1x+1- \frac{1}{x + 1}

      The result is: 1x+1+1x1- \frac{1}{x + 1} + \frac{1}{x - 1}

    The result is: (x2)(1x+1+1x1)+log(x1)log(x+1)\left(x - 2\right) \left(- \frac{1}{x + 1} + \frac{1}{x - 1}\right) + \log{\left(x - 1 \right)} - \log{\left(x + 1 \right)}

  2. Now simplify:

    2x+(x1)(x+1)(log(x1)log(x+1))4(x1)(x+1)\frac{2 x + \left(x - 1\right) \left(x + 1\right) \left(\log{\left(x - 1 \right)} - \log{\left(x + 1 \right)}\right) - 4}{\left(x - 1\right) \left(x + 1\right)}


The answer is:

2x+(x1)(x+1)(log(x1)log(x+1))4(x1)(x+1)\frac{2 x + \left(x - 1\right) \left(x + 1\right) \left(\log{\left(x - 1 \right)} - \log{\left(x + 1 \right)}\right) - 4}{\left(x - 1\right) \left(x + 1\right)}

The graph
02468-8-6-4-2-1010-2525
The first derivative [src]
                      /  1       1  \             
-log(x + 1) + (x - 2)*|----- - -----| + log(x - 1)
                      \x - 1   x + 1/             
(x2)(1x+1+1x1)+log(x1)log(x+1)\left(x - 2\right) \left(- \frac{1}{x + 1} + \frac{1}{x - 1}\right) + \log{\left(x - 1 \right)} - \log{\left(x + 1 \right)}
The second derivative [src]
    2       2               /   1           1    \
- ----- + ------ + (-2 + x)*|-------- - ---------|
  1 + x   -1 + x            |       2           2|
                            \(1 + x)    (-1 + x) /
(x2)(1(x+1)21(x1)2)2x+1+2x1\left(x - 2\right) \left(\frac{1}{\left(x + 1\right)^{2}} - \frac{1}{\left(x - 1\right)^{2}}\right) - \frac{2}{x + 1} + \frac{2}{x - 1}
The third derivative [src]
      3          3                  /   1           1    \
- --------- + -------- - 2*(-2 + x)*|-------- - ---------|
          2          2              |       3           3|
  (-1 + x)    (1 + x)               \(1 + x)    (-1 + x) /
2(x2)(1(x+1)31(x1)3)+3(x+1)23(x1)2- 2 \left(x - 2\right) \left(\frac{1}{\left(x + 1\right)^{3}} - \frac{1}{\left(x - 1\right)^{3}}\right) + \frac{3}{\left(x + 1\right)^{2}} - \frac{3}{\left(x - 1\right)^{2}}