Thanks a lot, Simon! Georg
On Wednesday, June 3, 2015 at 4:33:48 AM UTC+2, Simon King wrote: > > Hi Georg, > > On 2015-06-02, ggrafendorfer <georg.gra...@gmail.com <javascript:>> > wrote: > > sage: g(x) = x^2 - 26*x -9 > > sage: g.factor() > > x^2 - 26*x - 9 > > First of all, what you create is a symbolic function, so, factorisation > doesn't really make sense. > > sage: g(x) = x^2-26*x-9 > sage: g > x |--> x^2 - 26*x - 9 > > What you probably want to factor is a symbolic expression that isn't a > function. Let's see if it works: > > sage: g = x^2-26*x-9 > sage: g > x^2 - 26*x - 9 > sage: g.factor() > x^2 - 26*x - 9 > > This time, the reason is that your expression lives in the symbolic > ring, which is so large that the notion of factorisation doesn't really > make sense (you could factor g as, say sin(x)*(g/sin(x))). > > sage: g.parent() > Symbolic Ring > > So, instead of working with general symbolic expressions, you should > work with actual polynomials, living in a polynomial ring with > prescribed coefficient domain. > > Of course, the factorisation of your polynomial will depend on the > coefficient domain: > > sage: R.<x> = ZZ[] > sage: R > Univariate Polynomial Ring in x over Integer Ring > sage: g = x^2-26*x-9 > sage: g.factor() > x^2 - 26*x - 9 > > but when you work over the algebraic completion of QQ or if you work in > RR or some other large enough coefficient domain, then g factors: > > sage: R.<x> = QQbar[] > sage: g = x^2-26*x-9 > sage: g.factor() > (x - 26.34166406412634?) * (x + 0.3416640641263338?) > sage: R.<x> = RR[] > sage: g = x^2-26*x-9 > sage: g.factor() > (x - 26.3416640641263) * (x + 0.341664064126334) > > Best regards, > Simon > > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
