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Re: Fourth degree polynomial

  • To: mathgroup at
  • Subject: [mg29264] Re: [mg29251] Fourth degree polynomial
  • From: BobHanlon at
  • Date: Sat, 9 Jun 2001 03:08:51 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

In a message dated 2001/6/8 4:37:28 AM, Stephane.Redon at writes:

>I've got a fourth degree polynomial which I would like to break into two
>second order polynomials. Unfortunately, the Factor function doesn't manage
>to do it, probably because it attempts to find all the roots of my
>polynomial. Is there a way to do this WITHOUT finding the roots ?

Recommend that you give examples of problem

poly = (x^2+7x-39)(9x^2-5x-71)//Expand

9*x^4 + 58*x^3 - 457*x^2 - 302*x + 2769


(x^2 + 7*x - 39)*(9*x^2 - 5*x - 71)

If for some reason that doesn't work, you could use a brute force approach:

(a1*x^2+b1*x+c1)*(x^2+b2*x+c2) /. 
        CoefficientList[poly, x] == 
          CoefficientList[(a1*x^2+b1*x+c1)*(x^2+b2*x+c2), x]], {a1, b1, b2, 
        c1, c2}][[1]]

(x^2 + 7*x - 39)*(9*x^2 - 5*x - 71)

Bob Hanlon
Chantilly, VA  USA

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