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Poverseries error for 1/(1-t)^2 #1569

Closed rtoy closed 2 days ago

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 19:43:10 Created by *anonymous on 2003-05-16 16:15:52 Original: https://sourceforge.net/p/maxima/bugs/314

It seems powerseries(1(a-b*t)^n, t, 0) produces an error for n=2, but is correct for n=1,3,4:

(C1) POWERSERIES(1/(a-b*t)^2, t, 0);

           INF
           ====
           \       I1  - I1 - 2       I1

(D1) > a b (I1 + 1) t /

           I1 = 0

[I believe that powers of a and b above have opposite signs].

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 19:43:12 Created by nobody on 2003-05-17 18:32:39 Original: https://sourceforge.net/p/maxima/bugs/314/#dd78

Logged In: NO

(C1) verbose:true; (D1) TRUE (C2) POWERSERIES(1/(a-b*t)^2, t, 0);

In the first simplification we have returned: 1 -------------------- 2 2 2 b t - 2 a b t + a

trying to do a rational function expansion of 1 -------------------- 2 2 2 b t - 2 a b t + a Using a special rule for expressions of form M - N (A + C VAR )

Here we have [N = 2, A = - a, C = b, M = 1]

INF

\ I1 - I1 - 2 I1 (D2) > a b (I1 + 1) t /

I1 = 0 (C3)

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 19:43:15 Created by kratt5 on 2003-05-19 08:32:05 Original: https://sourceforge.net/p/maxima/bugs/314/#adbb

Logged In: YES user_id=651552

This is fixed with the fix for [727542] powerseries wrong/fix

Martin

(please, somebody merge it into cvs, it is IMPORTANT!)

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 19:43:19 Created by rtoy on 2003-05-28 16:41:08 Original: https://sourceforge.net/p/maxima/bugs/314/#8053

rtoy commented 2 days ago

Imported from SourceForge on 2024-07-04 19:43:22 Created by rtoy on 2003-05-28 16:41:09 Original: https://sourceforge.net/p/maxima/bugs/314/#0ce0

Logged In: YES user_id=28849

Bug marked as duplicate. I'll apply your patch for bug 727542.