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Integral of (3x+4)/(x+1) dx

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The solution

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  1           
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 |  3*x + 4   
 |  ------- dx
 |   x + 1    
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013x+4x+1dx\int\limits_{0}^{1} \frac{3 x + 4}{x + 1}\, dx
Integral((3*x + 4)/(x + 1), (x, 0, 1))
Detail solution
  1. There are multiple ways to do this integral.

    Method #1

    1. Let u=3xu = 3 x.

      Then let du=3dxdu = 3 dx and substitute dudu:

      u+4u+3du\int \frac{u + 4}{u + 3}\, du

      1. Let u=u+3u = u + 3.

        Then let du=dudu = du and substitute dudu:

        u+1udu\int \frac{u + 1}{u}\, du

        1. Rewrite the integrand:

          u+1u=1+1u\frac{u + 1}{u} = 1 + \frac{1}{u}

        2. Integrate term-by-term:

          1. The integral of a constant is the constant times the variable of integration:

            1du=u\int 1\, du = u

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

          The result is: u+log(u)u + \log{\left(u \right)}

        Now substitute uu back in:

        u+log(u+3)+3u + \log{\left(u + 3 \right)} + 3

      Now substitute uu back in:

      3x+log(3x+3)+33 x + \log{\left(3 x + 3 \right)} + 3

    Method #2

    1. Rewrite the integrand:

      3x+4x+1=3+1x+1\frac{3 x + 4}{x + 1} = 3 + \frac{1}{x + 1}

    2. Integrate term-by-term:

      1. The integral of a constant is the constant times the variable of integration:

        3dx=3x\int 3\, dx = 3 x

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

        Then let du=dxdu = dx and substitute dudu:

        1udu\int \frac{1}{u}\, du

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

        Now substitute uu back in:

        log(x+1)\log{\left(x + 1 \right)}

      The result is: 3x+log(x+1)3 x + \log{\left(x + 1 \right)}

    Method #3

    1. Rewrite the integrand:

      3x+4x+1=3xx+1+4x+1\frac{3 x + 4}{x + 1} = \frac{3 x}{x + 1} + \frac{4}{x + 1}

    2. Integrate term-by-term:

      1. The integral of a constant times a function is the constant times the integral of the function:

        3xx+1dx=3xx+1dx\int \frac{3 x}{x + 1}\, dx = 3 \int \frac{x}{x + 1}\, dx

        1. Rewrite the integrand:

          xx+1=11x+1\frac{x}{x + 1} = 1 - \frac{1}{x + 1}

        2. Integrate term-by-term:

          1. The integral of a constant is the constant times the variable of integration:

            1dx=x\int 1\, dx = x

          1. The integral of a constant times a function is the constant times the integral of the function:

            (1x+1)dx=1x+1dx\int \left(- \frac{1}{x + 1}\right)\, dx = - \int \frac{1}{x + 1}\, dx

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

              Then let du=dxdu = dx and substitute dudu:

              1udu\int \frac{1}{u}\, du

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

              Now substitute uu back in:

              log(x+1)\log{\left(x + 1 \right)}

            So, the result is: log(x+1)- \log{\left(x + 1 \right)}

          The result is: xlog(x+1)x - \log{\left(x + 1 \right)}

        So, the result is: 3x3log(x+1)3 x - 3 \log{\left(x + 1 \right)}

      1. The integral of a constant times a function is the constant times the integral of the function:

        4x+1dx=41x+1dx\int \frac{4}{x + 1}\, dx = 4 \int \frac{1}{x + 1}\, dx

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

          Then let du=dxdu = dx and substitute dudu:

          1udu\int \frac{1}{u}\, du

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

          Now substitute uu back in:

          log(x+1)\log{\left(x + 1 \right)}

        So, the result is: 4log(x+1)4 \log{\left(x + 1 \right)}

      The result is: 3x3log(x+1)+4log(x+1)3 x - 3 \log{\left(x + 1 \right)} + 4 \log{\left(x + 1 \right)}

  2. Add the constant of integration:

    3x+log(3x+3)+3+constant3 x + \log{\left(3 x + 3 \right)} + 3+ \mathrm{constant}


The answer is:

3x+log(3x+3)+3+constant3 x + \log{\left(3 x + 3 \right)} + 3+ \mathrm{constant}

The answer (Indefinite) [src]
  /                                       
 |                                        
 | 3*x + 4                                
 | ------- dx = 3 + C + 3*x + log(3 + 3*x)
 |  x + 1                                 
 |                                        
/                                         
3x+4x+1dx=C+3x+log(3x+3)+3\int \frac{3 x + 4}{x + 1}\, dx = C + 3 x + \log{\left(3 x + 3 \right)} + 3
The graph
0.001.000.100.200.300.400.500.600.700.800.9005
The answer [src]
3 + log(2)
log(2)+3\log{\left(2 \right)} + 3
=
=
3 + log(2)
log(2)+3\log{\left(2 \right)} + 3
3 + log(2)
Numerical answer [src]
3.69314718055995
3.69314718055995

    Use the examples entering the upper and lower limits of integration.