Posted by BioBabe on .
How would you factor 3x^34x^2+4x1?
P.S. Factor theorem does not work here.

12th grade Math? 
drwls,
Look for the first root by trial and error. Using the "q/p theorem", I see that one solution is +1/3. So, (x  1/3) is one factor.
Divide that into 3x^34x^2+4x1 to get a quadratic factor,
(3x^2 3x +3) = 3 (x^2 x +1).
The term in parentheses can be factored by the usual means, but gives two complex roots.
3x^34x^2+4x1 = 3(x 1/3)(x^2x+1)
(3x1)(x^2x+1)) 
12th grade Math? 
BioBabe,
What's the q/p theorem though?

12th grade Math? 
drwls,
I was afraid you'd ask me that :)
The more common name for it is the rational roots test (or theorem).
Here is a reference.
http://en.wikipedia.org/wiki/Rational_root_theorem
It doesn't always provide a root, but if there is a rational real root, it works.
Briefly, it says that if the constant term of the polynomial is q and the first term in p, and if there are rational real roots, one of the roots will be
+/ q/p or +/ the tio of primenumber factors of q and p. 
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eapmo dzywoakr,
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