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Problems computing area with integrals.

  1. Jan 29, 2009 #1
    1. The problem statement, all variables and given/known data

    Find the total area enclosed by the graphs of

    y=9x^2–x^3+x
    y=x^2+16x


    2. Relevant equations

    No real equations, just using integrals

    3. The attempt at a solution

    I graph the functions and find they intersect at 0 and 5, and that y=x^2+16x seems to be the upper function while y=9x^2-x^3+x is the lower function.

    I set up an integral with the lower limit 0 and the upper limit 5, and x^2+16x - (9x^2-x^3+x) dx inside the integral.

    I solve by simplifying and using the fundamental theorem of calculus and get 10.416. The homework website I'm using is telling me this is wrong...

    Thank you.
     
  2. jcsd
  3. Jan 29, 2009 #2

    Dick

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    Science Advisor
    Homework Helper

    They intersect at three points, not two. One is a cubic equation. Can you find them?
     
    Last edited: Jan 29, 2009
  4. Jan 29, 2009 #3
    I've checked it which sage and I get 10.416... I say forget what the website says.
     
  5. Jan 29, 2009 #4
    Nevermind. Follow Dick's advice.
     
  6. Jan 29, 2009 #5
    Found it and got the correct answer. Thanks a bunch!
     
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