Solving this integral in 2 different ways

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    Integral
In summary, the conversation discusses different methods of finding the integral of x/(2x-1)dx and how they result in different answers. The first method involves using substitution, while the second method involves using integration by parts. The speaker is unsure of where they went wrong in their second method, but the other person provides an explanation and reassurance that both methods are correct.
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dyn
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Homework Statement
integrate x/(2x-1) with respect to x
Relevant Equations
##\int \frac 1 x \, dx = \ln|x| ##
The answer gives $$ \int x /(2x-1)\ dx = x/2 +(1/4)ln|2x-1| + C $$ whicjh I can obtain. But when I try a different way I get a different answer. I must be making a stupid mistake but I can't see it. Here is my method
$$ \int x/(2x-1) dx = \int x/[2(x-(1/2)] dx = (1/2) \int x/(x-(1/2)) dx $$ $$= (1/2) \int (x-(1/2)+(1/2))/(x-(1/2)) dx = (1/2) \int 1+(1/2)/(x-(1/2))dx = x/2+(1/4)ln|x-(1/2)|+C$$
What is wrong with my method ? I just can't see it.
Thanks
 
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  • #2
## \ln|x-\frac{1}{2}|=\ln|(2x-1)/2|=\ln|2x-1|-\ln|2| =\ln|2x-1|+C' ##. What you did is equally correct.
 
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Thank you. That problem has been driving me crazy!
 
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1. 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 total amount of something, such as distance, volume, or probability, given a certain function.

2. Why would I need to solve an integral in 2 different ways?

Solving an integral in 2 different ways allows you to check your work and ensure that you have found the correct solution. It also helps to develop a deeper understanding of the mathematical concepts involved.

3. What are the two methods for solving integrals?

The two main methods for solving integrals are the substitution method and the integration by parts method. The substitution method involves substituting a new variable for the original variable in the integral, while the integration by parts method involves breaking down the integral into smaller, simpler parts.

4. How do I know which method to use for solving a particular integral?

The choice of method depends on the form of the integral. For integrals with a clearly defined function, the substitution method is usually more efficient. For integrals with products of functions, the integration by parts method is often the best approach.

5. How can I check my work when solving an integral in 2 different ways?

To check your work, you can plug your solutions back into the original integral and see if they produce the same result. You can also use online integral calculators or ask a colleague to review your work.

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