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Monocles

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**[SOLVED] integration by parts question**

## Homework Statement

This is part of a larger problem but I'm just not sure if I have the right answer.

edit: this is integral of ln(x-7)dx i just can't seem to figure out how to make it in latex

## Homework Equations

## The Attempt at a Solution

u-substituion:

[tex]u = x - 7[/tex]

[tex]du = dx[/tex]

Integration by parts to get

[tex]\intlnudu = ulnu - \int1du[/tex]

[tex] = ulnu - u[/tex]

[tex] = (x - 7)ln(x - 7) - (y - 7) + C[/tex]

Now my only problem with this answer is that it gives 7 + C as part of the answer, and I can't recall ever seeing a constant + C as the answer for any integral.

I actually plugged the equation into this integral finder:

http://integrals.wolfram.com/index.jsp

And it told me that it was

[tex](x-7)ln(x-7) - x[/tex]

I'm guessing the +C is a given.

I would just leave it at +C and go on but its part of a differential equation so the value of C ends up being important...

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