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Math Help - Easy integral problem

  1. #1
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    Easy integral problem

    How do you find the integral of sqrt[1+81x]? u-substitution and integration by parts does not seem to work.
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  2. #2
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    Quote Originally Posted by virtuoso735 View Post
    How do you find the integral of sqrt[1+81x]? u-substitution and integration by parts does not seem to work.
    It should \int\sqrt{1+81x}\,dx. Let u = 1 + 81x. Your problem reduce to \frac{1}{81} \int \sqrt{u}\, du
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  3. #3
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    On the contrary, u-sub does work. Try u = 1+81x

    But for such a trivial integral, it's best to see it as \frac{1}{81} \int \sqrt{1+81x}~d(1+81x) and integrate directly.

    Are you sure you did not mean \sqrt{1+81x^2} instead?
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