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[parisse]

Please do not post pictures, post commandlines instead, because that will spare time to all people who would like to try in the emulator since one can copy/paste commandlines.
The CAS *is* correct. Polynomial removable singularities are removed by efficient CAS, because otherwise you would never be able to do anything useful, you would loose all the time in special case handling (with combinatoric explosion of the number of special cases), and for nothing except perhaps for exercices that make math teachers happy to say to their student "You're wrong, it's not defined" :-)