Solving an integral, what to substitute

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In summary, the conversation discusses a problem with solving a given integral and asks for advice on what substitution to use. The suggested substitution is to let the new variable equal the integrand. The conversation also mentions a typo in the original integral but states that the same substitution would still work.
  • #1
beta3
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Hi

Recently I found an integral which I can't solve, I don't know or can't guess how and what to substitute.

[tex]\int_{\frac{3}{2}}^{2}(\frac{x-1}{3-2})^{\frac{1}{2}}dx[/tex]


Please tell me what you would substitute and why you would do that
Thanks


ps:
the solution isn't important to me, i want to understand and see how one can do that by oneself
 
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  • #2
I would start with the substitution 3 - 2 = 1.

This is really an easy problem if you think about it at all -- think of an integral that you can do that looks similar, and make a substitution that makes this integral look more like that integral.
 
  • #3
oh, I actually noticed, that I made a typo, the denominator is wrong

here is the right one:
[tex]\int_{\frac{3}{2}}^{2}(\frac{x-1}{3-x})^{\frac{1}{2}}dx[/tex]

still recomending the same substitution?
 
  • #4
The two substitutions that came to mind would still be two of the first things I'd try... I suspect still that both will work.
 
  • #5
Arguably, the simplest substitution is to let the new variable equal the integrand.
 

1. How do I know what to substitute when solving an integral?

The substitution method involves substituting a variable for the expression inside the integral. This variable should be chosen in such a way that it simplifies the integral and makes it easier to solve.

2. Can I substitute any variable for the expression inside the integral?

No, the variable you choose to substitute must be independent of the variable of integration. This means that it should not appear anywhere else in the integral other than the expression being substituted.

3. What is the purpose of substitution in solving an integral?

The main purpose of substitution is to simplify the integral and make it easier to solve. It allows us to rewrite the integral in terms of a different variable, which may be easier to integrate.

4. Is there a specific method for choosing the substitution variable?

Yes, there are several methods for choosing the substitution variable, such as using trigonometric identities, looking for patterns, or using a specific formula. It is important to choose a variable that simplifies the integral and makes it easier to solve.

5. Are there any common mistakes to avoid when using substitution to solve an integral?

Yes, some common mistakes to avoid include neglecting to substitute the differential term, choosing a substitution variable that is not independent of the variable of integration, and forgetting to apply the chain rule when differentiating the substituted variable. It is important to carefully consider the substitution and its implications before proceeding with solving the integral.

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