Friday
March 24, 2017

Post a New Question

Posted by on Monday, March 23, 2009 at 11:58am.

List the possible rational roots of 2x^3 + 17x^2 + 23x - 42 = 0

My answer: the possible rational roots are {±1, ±2, ±3, ±6, ±7, ±14, ±21, ±42. ±1/2, ±3/2, ± 7/2, ±21/2}.

Correct?

  • Advanced Math. - , Monday, March 23, 2009 at 1:08pm

    yes, and guess what?
    x = 1 works!

    after a quick synthetic division I got
    2x^3 + 17x^2 + 23x - 42 = 0
    (x-1)(x^2 + 19x + 42) = 0

    and that quadratic factors very nicely again.

  • Advanced Math. - , Monday, March 23, 2009 at 1:18pm

    Yes, this is what you get when you apply the Rational Roots theorem.

    But your list is very long, so it is of little use. It is a bit like answering the question by saying that all possible rational roots are the members of Q (as the problem didn't specifically say to list all the roots that the Rational Roots theorem yields).

  • Advanced Math. - , Wednesday, October 31, 2012 at 5:30pm

    Incorrect

Answer This Question

First Name:
School Subject:
Answer:

Related Questions

More Related Questions

Post a New Question