Quantcast

Got Homework?

Connect with other students for help. It's a free community.

  • across
    MIT Grad Student
    Online now
  • laura*
    Helped 1,000 students
    Online now
  • Hero
    College Math Guru
    Online now

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

DeadShot Group Title

Which of the following is a polynomial with roots - square root of 5, square root of 5, and -3 ? x3 - 2x2 - 3x + 6, x3 + 2x2 - 3x - 6, x3 - 3x2 - 5x + 15, or x3 + 3x2 - 5x - 15?

  • one year ago
  • one year ago

  • This Question is Closed
  1. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    If you have roots of: a, b, and c your polynomial has the form: (x - a)(x - b)(x - c) = 0 Substitute a, b, and c for the given roots and multiply the expression out on the left side.

    • one year ago
  2. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    x^3 -2.25x^2+2.25x^2-3x2-2.25x+2.25x-3x-15

    • one year ago
  3. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    simplified, it's x^3-3x^2-3x-15, right?

    • one year ago
  4. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    You wouldn't even have to ask that last question because you have 4 choices and this choice is not even listed among them. Here's a hint on how to expand that expression I gave you: (x - a)(x - b)(x - c) = 0 [(x - a)(x - b)](x - c) = 0 [x^2 - (a + b)x + ab](x - c) = 0 [x^2 - (a + b)x + ab]x - [x^2 - (a + b)x + ab]c = 0

    • one year ago
  5. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    [x^2-(-2.25+2.25)x + (-2.25)*2.25]x-[x^2-(-2.25+2.25)x + (-2.25)*2.25]-3=0

    • one year ago
  6. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    Where are you getting +-2.25 from? Neither has anything to do with sqrt(5).

    • one year ago
  7. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    sqrt(5) is approx 2.25

    • one year ago
  8. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    You don't want to be working with approximations here.

    • one year ago
  9. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    ok

    • one year ago
  10. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    x^3 - 3x^2 - 5x + 15

    • one year ago
  11. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    I would suggest evaluating the following first: [x - sqrt(5)][x + sqrt(5)] That correspond to the leftmost factors. Get that down to a trinomial.

    • one year ago
  12. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    that would be x^2-5

    • one year ago
  13. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    (x^2-5) (x-3)=x^3 - 3x^2 - 5x + 15

    • one year ago
  14. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    right?

    • one year ago
  15. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    The third root is "-3", so you have: [x - (-3)] or (x + 3) for that third factor. I think that's where you having your trouble. When you subtract a negative, it's like adding a positive.

    • one year ago
  16. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    So, taking up from where you were writing: (x^2 - 5)(x + 3) = 0 And then expand that. You are very close to your answer now.

    • one year ago
  17. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    so, it's x^3+3x^2-5x-15?

    • one year ago
  18. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    Yes! Excellent! Just remember about subtracting negatives and you will be ok.

    • one year ago
  19. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    Okay, Thanks for the help!

    • one year ago
  20. tcarroll010 Group Title
    Best Response
    You've already chosen the best response.
    Medals 1

    You're welcome! Good luck to you in all of your studies and thx for the recognition! @DeadShot

    • one year ago
  21. DeadShot Group Title
    Best Response
    You've already chosen the best response.
    Medals 0

    No problem!

    • one year ago
    • Attachments:

See more questions >>>

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.