Double integral problem (pretty basic)

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SUMMARY

The discussion centers on solving the double integral problem defined as \(\int\int_{R}\frac{x}{1+xy} dA\) over the region \(R = [0,1] \times [0,1]\). The initial approach involved converting it into an iterated integral \(\int^{1}_{0}\int^{1}_{0}\frac{x}{1+xy} dx dy\), but the user struggled with integration techniques. A pivotal suggestion was to integrate with respect to \(y\) first, which proved to be a crucial step in simplifying the problem and achieving a solution.

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  • Understanding of double integrals in multivariable calculus
  • Familiarity with iterated integrals and their evaluation
  • Knowledge of u-substitution in integration
  • Basic skills in polynomial long division
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  • Practice solving double integrals using different orders of integration
  • Study the method of u-substitution in greater detail
  • Learn polynomial long division techniques for simplifying integrands
  • Explore additional resources on multivariable calculus integration techniques
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Students in multivariable calculus, particularly those struggling with integration techniques, as well as educators looking for common challenges faced by learners in this subject area.

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Good day, all:

We recently hit double/triple integrals in my multivariable calculus course and I have found that my integration abilities are, well, *beyond* rusty ... and so the problem below, which is one of the very first on my current problem set, has me stumped.

Homework Statement



\int\int_{R}\frac{x}{1+xy} dA R = { [0,1]x[0,1] = {(x,y): 0 \leq x \leq1, 0 \leq y \leq1 }

The Attempt at a Solution



My first and nearly only step was to turn this into an iterated integral:

\int^{1}_{0}\int^{1}_{0}\frac{x}{1+xy} dx dy

... and this is where I begin to choke and sputter. I have started to try u-substitution on this with u = 1+xy, but didn't get anything that made sense to me; some hints I have found online seem to indicate that I should be able to perform "polynomial long division" to turn this into a sum or difference of two simpler integrals, but I guess I don't sufficiently understand polynomial long division to carry this out here.

Any hints would be much appreciated. I am considering dropping this course, but I would like to avoid that ... I need some serious integration mojo to be directly infused into my skull asap. :bugeye:

Regards,

Glenn
 
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Did you try integrating with respect to y first?
 
murmillo said:
Did you try integrating with respect to y first?

No. I'll check it out and see what happens. Thank you.

EDIT: That was key, of course. Jeez. ::strikes forehead::
 
Last edited:

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