Quantcast

A community for students. Sign up today!

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

patbatE21

  • 3 years ago

Integrate (9 - x^2 - x -1)dy from x = -1 to x = 2

  • This Question is Closed
  1. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    what problem exactly do you have with this integral?

  2. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    well the I'm actually trying to sketch a region enclosed by given curves

  3. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    but i think there is something wrong with my integration...so far I have 9y -1/3y^3 -1/2y^2 - y

  4. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    first off I assume you mean (9 - x^2 - x -1)dx

  5. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yes

  6. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    so then you answer is correct if you replace y's with x's

  7. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    the actual question is " Sketch the region enclosed by the given curves. Decide whether to integrate with respect to x or y. Draw a typical approximating rectangle and label its height and width. Then find the area of the region

  8. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    y = x + 1, y = 9 - x^2, x = -1, x = 2

  9. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I am just having issues finding the area

  10. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    let's just do the integral first, yeah?

  11. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    ok

  12. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I know that I will have to take the integral [f(y) -g(y)] from c to d

  13. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    It's f(x)-g(x) I think you are having a problem keeping track of variables, remember y=f(x), so f(y) is something different and undefined here.

  14. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I believe that is my problem, understood

  15. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    so your integral is\[\int\limits_{-1}^{2}9-x^2-x-1dx\]

  16. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Alright, I'm so far

  17. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    your answer is right replaced with x's\[9x-{1\over3}x^3-{1\over2}x^2-x\]evaluated from -1 to 2, what do you get?

  18. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    19.2

  19. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    let me try! lol

  20. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    lol ok

  21. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Sorry 19.5 Just the evaluation, right? As you see I hate that too, here's a site, if you don't already know it that's good for that. http://www.wolframalpha.com/ and here's your particular problem http://www.wolframalpha.com/input/?i=Integrate+%289+-+x%5E2+-+x+-1%29dx+from+-1+to+2

  22. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Thank you so much

  23. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    wait a minute this is all wrong! I should have noticed sooner!

  24. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    No its correct I just submitted it online and it is marked correct

  25. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    did you mean it as you typed it? 9 - x^2 - x -1 are you mot missing an x? because 9-1=8 so the integration we di is wrong

  26. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    yes thats correct

  27. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    I see what you mean, but how is it still correct

  28. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Okay it's not ALL wrong, but the way wee did it is silly, it may be right, but we failed to notice that \[9 - x^2 - x -1=8-x^2-x\] So we integrated an extra term. It is important to see shortcuts like that, so at least look for those in the future :)

  29. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Ok, the ah-hah moments in math...such a wonderful subject

  30. patbatE21
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    Thanks once again

  31. TuringTest
    • 3 years ago
    Best Response
    You've already chosen the best response.
    Medals 1

    very welcome!

  32. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Ask a Question
Find more explanations on OpenStudy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.