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Re: Taking LCM in a polynomial expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg95402] Re: Taking LCM in a polynomial expression
  • From: m.r at inbox.ru
  • Date: Sat, 17 Jan 2009 05:32:22 -0500 (EST)
  • References: <gkn5pa$iob$1@smc.vnet.net>

Srikanth wrote:
> Hi
> I have a symbolic matrix that I invert. When I take each individual
> entry of the resulting matrix, I get an expression of the form:
> num1/den1 + num2/den1 + .... + num_n/den1
> where den1 is the determinant of the matrix. I'd like to get an
> expression of the form:
> Num/Den.
>
> I tried using Simplify (as well as multiplying the matrix by its
> determinant), but it doesn't seem to help. Any suggestions?
>
> On a related note, the final Num is a polynomial in two variables -
> say x,y. I'd like to arrange it in decreasing powers of x - like f1(y)
> x^n + f2(y) x^n-1... + constant. What function should use? Is there
> any way to both in a single step?
>
> Thanks a lot
> Srikanth

As mentioned in tutorial/PolynomialOrderings, in version 7 it's
possible to control the sorting of polynomial terms/factors to some
extent in TraditionalForm output:

In[1]:= x y^2 + x^2 y + 1 // TraditionalForm[#, ParameterVariables :>
{y}]&

Out[1]//TraditionalForm= y x^2+y^2 x+1

Maxim Rytin
m.r at inbox.ru


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