#840 factor((x^15+1)^15-(x^15-1)^15) wrong

closed
nobody
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5
2008-05-25
2005-12-19
No

factor((x^15+1)^15-(x^15-1)^15) gives:
30 180 150 120
2 (3 x + 1) (5 x + 150 x + 951 x
90 60 30
+ 1828 x + 1059 x + 102 x + 1)

However, the second factor is composite, it is
(5*x^60 + 10*x^30 + 1)*
(x^120 + 28*x^90 + 134*x^60+ 92*x^30 +1)

This happens on Maxima 5.9.2 on AMD64 using Clisp
and on 5.9.1 using gcl (both AMD64 and i386)

Discussion

  • Dan Gildea

    Dan Gildea - 2008-05-25
    • status: open --> closed
     
  • Dan Gildea

    Dan Gildea - 2008-05-25

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    fixed in src/factor.lisp rev 1.17
    o nprod: loop structure: was returning after finding factor when no tuples
    left, rather than continuing to next stage/tloop.

    (%i21) factor((x^15+1)^15-(x^15-1)^15) ;
    (%o21) 2*(3*x^30+1)*(5*x^60+10*x^30+1)*(x^120+28*x^90+134*x^60+92*x^30+1)

     

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