A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • 5 years ago

how do you find the rational and real roots? x^7+3x^6-5x^2-3x-5=0

  • This Question is Closed
  1. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    trial and error.. alot of it lol

  2. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    possible rational roots?

  3. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    last# ----- helps to narrow it down fisrt#

  4. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Rational root test, fundamental theorem of algebra, synthetic division

  5. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i was thinking of writing a javascript to solve these things ;)

  6. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    make a fraction, numerator must divide 5, denom must divide 1, so only choices are \[\pm1, \pm 5\]

  7. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    if you can write javascript to find the roots of a poly of degree 7 you would be world famous and galois would have been mistaken.

  8. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    no, not all the roots; but the integer and rational roots that could be determined from this lol

  9. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i know i am being silly. you meant to find possible rational roots.

  10. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    how do you find the real roots?

  11. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    might be able to work it inside out and complete squares to find all roots .... i wonder

  12. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    there is no algorithm for finding the roots of a poly of degree seven.

  13. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    only 1 - 4. that is it. and the one for 3 is a page and the one for 4 is a wall.

  14. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    well, you could do the Newton Rhapsody method to find 1 root and narrow it down ..... perhaps ?

  15. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    i would try 1, -1, 5 and -5 and see if any work. then you can use synthetic division to reduce. i can see that 1 does not work since \[f(1)=1+3-5-2-5\]

  16. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    make sure you include your zero place holders

  17. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[f(-1)=-1+3-5+3-5=-1\]

  18. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    well we have to find one first.

  19. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    if you have a decent calculator check \[f(5)\]

  20. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    syntheitc can find them as well; but brute calculating is always a good option lol

  21. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    ok i will divide see if i get 0

  22. watchmath
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    Newton-Rhapsody :D :D

  23. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    newton rhapsody in blue

  24. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    5 doesn't work

  25. anonymous
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    and neither does -5 unless i made a mistake

  26. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    -5| 1x^7 +3x^6 +0 +0 +0 -5x^2 -3x -5 0 -5 10 -50 250 -1250 6275 ------------------------------------- 1 -2 10 -50 250 -1255 ...... no mistake lol

  27. amistre64
    • 5 years ago
    Best Response
    You've already chosen the best response.
    Medals 0

    D's sign change tells us what ...... do we include zeros as a sign change?

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

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

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.