Solving $\displaystyle \int \frac{\ln\left(x^2+2\right)}{(x+2)^2}dx$ by Parts

In summary, the conversation discusses the integration of the function $\frac{\ln(x^2+2)}{(x+2)^2}$ through the use of integration by parts, and the question of whether there is another method besides partial fraction decomposition to solve the integral $\int \frac{x}{(x^2+2)(x+2)}dx$. The participants ultimately agree that partial fraction decomposition is the best course of action, but also encourage exploring alternative methods as a means of building creativity in mathematics.
  • #1
juantheron
247
1
$\displaystyle \int \frac{\ln\left(x^2+2\right)}{(x+2)^2}dx$

$\bf{My\; Try::}$ Given $\displaystyle \int \ln \left(x^2+2\right)\cdot \frac{1}{(x+2)^2}dx$

Using Integration by parts, we get

$\displaystyle = -\ln\left(x^2+2\right)\cdot \frac{1}{(x+2)} + 2\int \frac{x}{\left(x^2+2\right)\cdot (x+2)}dx$

Is there is any other method by which we can solve the Integral

$\displaystyle \int \frac{x}{\left(x^2+2\right)\cdot (x+2)}dx$ other then partial fraction.

Help me

Thanks
 
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  • #2
Why the aversion to partial fraction decomposition? I think it is the best course of action for continuing. :D
 
  • #3
I agree with Mark, the best strategy would be partial fractions.

Try $\displaystyle \begin{align*} \frac{A\,x + B}{x^2 + 2} + \frac{C}{x + 2} \equiv \frac{x}{ \left( x^2 + 2 \right) \left( x + 2 \right) } \end{align*}$ for your partial fraction decomposition.
 
  • #4
Thanks Markfl and prove it.
 
  • #5
While partial fractions is fine/the standard way, asking for an alternative way is something I feel should always be encouraged (and never discouraged) in mathematics. Looking for alternative ways to do problems builds one's creativity far better than sticking to the usual methods.
 

FAQ: Solving $\displaystyle \int \frac{\ln\left(x^2+2\right)}{(x+2)^2}dx$ by Parts

What is the general process for solving integrals by parts?

The general process for solving integrals by parts involves using the formula ∫u dv = uv - ∫v du, where u and v are functions of x. The goal is to choose u and dv in a way that simplifies the integral and makes it easier to solve.

How do you choose which part to integrate and which part to differentiate?

When using the formula for integration by parts, the choice of u and dv is crucial. A common approach is to choose u as the part of the integrand that becomes simpler when differentiated, and dv as the part that becomes easier to integrate. This usually involves choosing u to be a polynomial or a function with simpler derivatives, and dv to be a more complicated function, such as a logarithm or trigonometric function.

Can this integral be solved using other integration techniques?

Yes, this integral can also be solved using substitution, which involves substituting a variable in the integral with a new variable and then solving the resulting integral. However, in some cases, integration by parts may be a more efficient method.

What are some common mistakes to avoid when using integration by parts?

One common mistake is forgetting to use the formula correctly, particularly when it comes to the signs. Another mistake is choosing the wrong parts to integrate and differentiate, which can result in a more complicated integral. It's also important to be careful with algebraic manipulation and to double check the final answer.

How can I check my answer for this integral?

You can check your answer by differentiating the solution and comparing it to the original integrand. You can also use a graphing calculator to graph the integrand and the antiderivative to visually confirm that they are the same.

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