A little refactoring in Pow.nseries().
A little refactoring in Pow.nseries().

This makes the code more robust and also shorter. Basically, when one has

e = 1+y+x+x**2
prefactor = 1+y

then it's better to use

(e - prefactor)/prefactor

rather than

e/prefactor - 1

because we will then have problems with simplification:

-1 + 1/(1+y) + y/(1+y) + x/(1+y) ....

while in the first case we get immediatelly

x/(1+y)

rahuldan/sympy,sahmed95/sympy,vipulroxx/sympy,Arafatk/sympy,MridulS/sympy,madan96/sympy,Designist/sympy,Sumith1896/sympy,kaushik94/sympy,minrk/sympy,jbbskinny/sympy,ahhda/sympy,postvakje/sympy,Davidjohnwilson/sympy,shipci/sympy,atreyv/sympy,sahmed95/sympy,shikil/sympy,ahhda/sympy,sunny94/temp,ga7g08/sympy,kaichogami/sympy,emon10005/sympy,AkademieOlympia/sympy,bukzor/sympy,AunShiLord/sympy,atreyv/sympy,beni55/sympy,ChristinaZografou/sympy,mafiya69/sympy,KevinGoodsell/sympy,cccfran/sympy,kaichogami/sympy,atreyv/sympy,Shaswat27/sympy,wyom/sympy,kmacinnis/sympy,drufat/sympy,souravsingh/sympy,oliverlee/sympy,jerli/sympy,liangjiaxing/sympy,MridulS/sympy,Davidjohnwilson/sympy,Sumith1896/sympy,chaffra/sympy,ga7g08/sympy,shikil/sympy,minrk/sympy,abloomston/sympy,AunShiLord/sympy,Gadal/sympy,pandeyadarsh/sympy,asm666/sympy,saurabhjn76/sympy,yashsharan/sympy,AkademieOlympia/sympy,MechCoder/sympy,toolforger/sympy,saurabhjn76/sympy,kaushik94/sympy,vipulroxx/sympy,abhiii5459/sympy,Arafatk/sympy,MechCoder/sympy,Curious72/sympy,iamutkarshtiwari/sympy,abhiii5459/sympy,hrashk/sympy,saurabhjn76/sympy,meghana1995/sympy,yashsharan/sympy,shipci/sympy,debugger22/sympy,mcdaniel67/sympy,jamesblunt/sympy,Shaswat27/sympy,postvakje/sympy,kevalds51/sympy,kevalds51/sympy,amitjamadagni/sympy,beni55/sympy,maniteja123/sympy,moble/sympy,atsao72/sympy,mcdaniel67/sympy,aktech/sympy,hrashk/sympy,souravsingh/sympy,pbrady/sympy,rahuldan/sympy,Designist/sympy,hargup/sympy,oliverlee/sympy,lindsayad/sympy,hargup/sympy,skidzo/sympy,farhaanbukhsh/sympy,sunny94/temp,lidavidm/sympy,mattpap/sympy-polys,amitjamadagni/sympy,dqnykamp/sympy,souravsingh/sympy,skirpichev/omg,srjoglekar246/sympy,chaffra/sympy,kumarkrishna/sympy,jamesblunt/sympy,debugger22/sympy,Gadal/sympy,sunny94/temp,mafiya69/sympy,Vishluck/sympy,Curious72/sympy,Designist/sympy,kmacinnis/sympy,asm666/sympy,sampadsaha5/sympy,oliverlee/sympy,bukzor/sympy,moble/sympy,garvitr/sympy,Vishluck/sympy,grevutiu-gabriel/sympy,garvitr/sympy,atsao72/sympy,atsao72/sympy,fperez/sympy,hargup/sympy,wanglongqi/sympy,pernici/sympy,jbaayen/sympy,yashsharan/sympy,rahuldan/sympy,Mitchkoens/sympy,maniteja123/sympy,jaimahajan1997/sympy,abloomston/sympy,wyom/sympy,cccfran/sympy,meghana1995/sympy,lidavidm/sympy,AkademieOlympia/sympy,jerli/sympy,kaichogami/sympy,postvakje/sympy,abhiii5459/sympy,moble/sympy,jaimahajan1997/sympy,pandeyadarsh/sympy,Shaswat27/sympy,ChristinaZografou/sympy,kumarkrishna/sympy,ChristinaZografou/sympy,VaibhavAgarwalVA/sympy,liangjiaxing/sympy,shipci/sympy,debugger22/sympy,madan96/sympy,jerli/sympy,grevutiu-gabriel/sympy,Curious72/sympy,mafiya69/sympy,pbrady/sympy,mcdaniel67/sympy,lindsayad/sympy,bukzor/sympy,maniteja123/sympy,chaffra/sympy,yukoba/sympy,liangjiaxing/sympy,AunShiLord/sympy,VaibhavAgarwalVA/sympy,shikil/sympy,abloomston/sympy,lidavidm/sympy,cswiercz/sympy,ga7g08/sympy,dqnykamp/sympy,sahmed95/sympy,Titan-C/sympy,toolforger/sympy,jaimahajan1997/sympy,hazelnusse/sympy-old,sahilshekhawat/sympy,pbrady/sympy,MechCoder/sympy,jamesblunt/sympy,sahilshekhawat/sympy,emon10005/sympy,toolforger/sympy,kevalds51/sympy,kumarkrishna/sympy,kaushik94/sympy,farhaanbukhsh/sympy,drufat/sympy,Titan-C/sympy,yukoba/sympy,cccfran/sympy,wanglongqi/sympy,Davidjohnwilson/sympy,wanglongqi/sympy,wyom/sympy,meghana1995/sympy,MridulS/sympy,kmacinnis/sympy,Mitchkoens/sympy,Mitchkoens/sympy,lindsayad/sympy,sampadsaha5/sympy,beni55/sympy,flacjacket/sympy,cswiercz/sympy,Gadal/sympy,asm666/sympy,cswiercz/sympy,sahilshekhawat/sympy,iamutkarshtiwari/sympy,skidzo/sympy,ahhda/sympy,madan96/sympy,Vishluck/sympy,sampadsaha5/sympy,hrashk/sympy,garvitr/sympy,grevutiu-gabriel/sympy,Arafatk/sympy,yukoba/sympy,ryanGT/sympy,farhaanbukhsh/sympy,Sumith1896/sympy,drufat/sympy,hazelnusse/sympy-old,Titan-C/sympy,dqnykamp/sympy,pandeyadarsh/sympy,iamutkarshtiwari/sympy,jbbskinny/sympy,aktech/sympy,tovrstra/sympy,jbbskinny/sympy,emon10005/sympy,aktech/sympy,skidzo/sympy,vipulroxx/sympy,VaibhavAgarwalVA/sympy,diofant/diofant