Integration by partial fractions part. 2

In summary, To solve the given integral, one can use the substitution method by letting u=e^x and then applying partial fractions. This will result in a final expression of (u du) / [(u-2)(u^2 + 1)].
  • #1
sdoyle
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0

Homework Statement


[tex]\int\frac{e^x}{(e^x-2)(e^2x +1)}[/tex] it should be e to the power of 2x



Homework Equations


Using substitution u=e^x, and then using partial fractions



The Attempt at a Solution


I have done this problem two separate ways. One with substitution and then partial fractions, and the other with just partial fractions. Both times I end with different coefficient values. I'm not sure if you can use both substitution and then partial fractions...
 
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  • #2
In your equation (which I can't really read) you're missing the dx! What I recommend you do is a u substitution, but make sure you change all the things related to x to u. For example, u = e^x, then du = e^x * dx so when you substitute the e^2x on top becomes e^x (since one of them is used for the du) giving you:

(u du) / [(u-2)(u^2 + 1)]
 

1. What is the purpose of using integration by partial fractions?

Integration by partial fractions is a technique used to simplify the integration of rational functions. It allows us to break down a complex fraction into simpler fractions that can be integrated easily.

2. How do you know when to use integration by partial fractions?

You can use integration by partial fractions when the degree of the numerator is less than the degree of the denominator of a rational function. It can also be used when the denominator can be factored into distinct linear or quadratic factors.

3. What are the steps for integrating by partial fractions?

The steps for integrating by partial fractions include:
1. Write the rational function in the form of a sum of simpler fractions.
2. Determine the unknown coefficients by equating the numerators of the simpler fractions with the original numerator.
3. Write the resulting fractions as separate integrals.
4. Evaluate each integral and combine them to get the final answer.

4. Can integration by partial fractions be used for improper fractions?

Yes, integration by partial fractions can be used for improper fractions. The resulting simpler fractions may have polynomials with higher degrees, but the integration can still be performed using the same steps as for proper fractions.

5. Are there any restrictions for using integration by partial fractions?

There are a few restrictions for using integration by partial fractions. The rational function must be proper, meaning that the degree of the numerator must be less than the degree of the denominator. Additionally, the denominator must be factorable into distinct linear or quadratic factors. If these conditions are not met, other techniques may need to be used for integration.

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