How can I integrate this using partial fractions?

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In summary, the conversation discusses using partial fractions to solve the integral of (3x^4+4x^3+16x^2+20x+9)/(x^5+2x^4+6x^3+12x^2+9x+18). The participants suggest using techniques such as expanding and factoring to simplify the problem. It is also mentioned that the solution involves using ln and 2/(x^2+3).
  • #1
Adventurehero
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[tex]\int\frac{3x^4+4x^3+16x^2+20x+9}{x^5+2x^4+6x^3+12x^2+9x+18}dx[/tex]

I tried using du/u for Lnu but I couldn't get it into that form. I don't have any idea what to do next, really. Can someone point me in the right direction?
 
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  • #2
You should try expanding it via partial fractions. There should be a section in your textbook about this.
 
  • #3
I would have sworn that denominator couldn't be factored, but it can!
 
  • #4
take u = (x^5+2x^4+6x^3+12x^2+9x+18)
du = 5x^4+8x^3+18x^2+24x+9
then take the numerator & cancel it out with du.
 
  • #5
What?

I'm having trouble factoring it, and I'm not sure what Nachore means.
 
  • #6
Use Kramer on the denominator, you will find that -2 is a root.
The remaining part can be factorized easily.
Then use partial fractions to split the integral into more classical ones.

This is not a particularly difficult integral, although a very tedious one to solve.
You might say that this makes it a difficult one after all.

Edit: It is not as tedious as I thought at first, the solution is ln(x+2)+ln(x^2+3)-2/(x^2+3)+C
 
Last edited:
  • #7
Nachore said:
take u = (x^5+2x^4+6x^3+12x^2+9x+18)
du = (5x^4+8x^3+18x^2+24x+9)dx
then take the numerator & cancel it out with du.
Yes, that's true. but since the numerator is nothing like that, it doesn't help at all!
 
  • #8
I get (x+2)(x^2+3)^2 as the bottom, factored out. Is this correct? I'm really not good at factoring.
 
  • #9
Yes, that's correct. Now use partial fractions.
 

1. How do I integrate this equation?

To integrate an equation, you need to follow the steps of the integration process. First, identify the function and its variables. Then, use the appropriate integration rules and techniques to solve for the indefinite integral. Finally, add any necessary constants to the solution to get the final answer.

2. What is the difference between definite and indefinite integration?

Definite integration involves finding the area under a curve between specific limits. It results in a numerical value. Indefinite integration, on the other hand, involves finding a general antiderivative of a function. It results in an expression with a constant term.

3. How do I know which integration technique to use?

There are several integration techniques, such as substitution, integration by parts, and trigonometric substitution. The best technique to use depends on the form of the function being integrated. It is important to practice and familiarize yourself with each technique to determine which one is most appropriate for a given problem.

4. Can I use a calculator to do integrals?

Yes, most scientific calculators have a built-in integration function. However, it is important to understand the integration process and techniques in order to properly use the calculator and interpret the results.

5. How do I check my answer after integrating?

You can check your answer by taking the derivative of the integrated function and comparing it to the original function. If the derivative matches the original function, then your integration is correct. You can also use online integration calculators or ask a friend or colleague to check your work.

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