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Homework Help: Integral Question

  1. Feb 15, 2010 #1
    1. The problem statement, all variables and given/known data

    Evaluate the integral INT sqrt(x^2+6x) dx

    3. The attempt at a solution

    I honestly have no clue how to even start. I know it involves trigonometric substitution, but I just can't solve it.

    Please Help?
     
  2. jcsd
  3. Feb 15, 2010 #2

    Mark44

    Staff: Mentor

    Complete the square.
    x^2 + 6x + 9 - 9 = (x + 3)^2 - 3^2.

    Now you're set to do a trig substitution. I always draw a triangle, since I don't want to clutter up my brain with what formula goes with what substitution. In that case, the hypotenuse should be x + 3, and either the opposite or adjacent side should be 3.
     
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