Homework Help: Advanced Math.

Posted by Jamie 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 {ą1, ą2, ą3, ą6, ą7, ą14, ą21, ą42. ą1/2, ą3/2, ą 7/2, ą21/2}.

Correct?

Advanced Math. - Reiny, 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. - Count Iblis, 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. - Bartolo Windu, Wednesday, October 31, 2012 at 5:30pm
Incorrect

Answer this Question

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