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Forcing a Polynomial Factor (Posted on 2013-08-03) Difficulty: 3 of 5
Find the values for a and b to force the polynomial x10 + ax5 + b to have x2+2x+3 as a factor.

  Submitted by Brian Smith    
Rating: 4.0000 (1 votes)
Solution: (Hide)
x^10/(x^2+2x+3) has a remainder of 22x-219, then x^10-22x+219 has x^2+2x+3 as a factor.

x^5/(x^2+2x+3) has a remainder of -11x-12, then x^5+11x+12 has x^2+2x+3 as a factor.

Now to find a and b: the expression x^10-22x+219 + a(x^5+11x+12) must have the linear term drop out. a=2 does that. Then x^10-22x+219 + a(x^5+11x+12) = x^10 + 2x^5 + 243.

The answer is a=2, b=243. To check (x^10+2x^5+243)/(x^2+2x+3) = x^8-2x^7+x^6+4x^5-11x^4+12x^3+9x^2-54x+81.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
re(2): Another approachSteve Herman2013-08-04 23:21:39
re: Another approachLarry2013-08-04 20:05:43
Another approachSteve Herman2013-08-04 15:34:09
solutionDaniel2013-08-03 22:45:59
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