Help with Integral: \int \frac{\(x+9}{x^2+9} dx

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In summary, an integral is used to find the cumulative sum of small values under a curve on a graph. To solve an integral, you need to find the antiderivative of the given function using integration techniques such as substitution or integration by parts. The given integral is asking for the antiderivative of a specific function, and the process for solving it involves substitution and using the rule for finding the antiderivative. There are restrictions for solving this integral, such as avoiding undefined values and using a different substitution if necessary.
  • #1
laker88116
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[tex] \int \frac{\(x+9}{x^2+9} dx [/tex]

I am not sure where to start. I have a feeling that I need to subsitute twice, but I just don't know what to use first. Any help is appreciated.
 
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  • #2
Try

[tex] \int \frac{x dx}{x^{2}+9} + 9 \int \frac{dx}{x^{2}+9} [/tex]
 
  • #3
Wow, that changes everything, ln and tan inverse I think just looking at it, let me try this, I can't believe I overlooked that.
 
  • #4
Yea, I solved it, thank you for the help.
 

What is an integral?

An integral is a mathematical concept that represents the area under a curve on a graph. It is used to find the cumulative sum of infinitely small values over a given interval. It is the inverse operation of differentiation.

How do I solve an integral?

To solve an integral, you need to find the antiderivative of the given function. This can be done by using integration techniques such as substitution, integration by parts, or using a table of integrals. Once you have found the antiderivative, you can evaluate the integral at the given limits to find the final answer.

What is the given integral asking for?

The given integral is asking for the antiderivative of the function \frac{x+9}{x^2+9}. This means that we need to find a function whose derivative is equal to \frac{x+9}{x^2+9}.

What is the process for solving this specific integral?

To solve \int \frac{x+9}{x^2+9} dx, we can first use the substitution u = x^2+9. This will give us du = 2x dx, which we can use to replace x dx in the original integral. This will result in \frac{1}{2}\int \frac{1}{u} du. We can then use the rule \int \frac{1}{u} du = \ln u + C to find the antiderivative. Finally, we can substitute back u = x^2+9 to get the final answer of \frac{1}{2}\ln(x^2+9) + C.

Are there any special cases or restrictions for solving this integral?

Yes, there are some restrictions for solving this integral. The function \frac{x+9}{x^2+9} is undefined at x = \pm 3 because it results in a division by zero. Therefore, the limits of integration must not include these values. Additionally, the substitution u = x^2+9 only works for x \neq \pm 3. If the limits of integration do include these values, a different substitution or integration technique must be used.

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