# Rearrange equation with mathematica s.t. variable only in denominator?

Posted 8 years ago
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 Hej all,I am struggling with an equation which I would like to rearrange so that the variable is in the denominator only. I tried combinations of many possible ways to put expression in different forms https://reference.wolfram.com/language/tutorial/PuttingExpressionsIntoDifferentForms.html but nothing worked out so far.Is there any possibility to tell mathematica to do it? (file attached)Thanks in advance. I would be very happy if you have an idea how to solve thisBest, Chris Attachments:
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Posted 8 years ago
 How about d = Denominator[f[x]]; Map[Inactive[Divide][#/x^Exponent[#, x], d/x^Exponent[#, x]] &, Collect[d*f[x], x]] It uses Inactive of Mathematica 10 to avoid re-arrangements of numerators and denominators.
Posted 8 years ago
 Hi all,thanks for your help. I did not manage to solve the problem in the way I wanted and did it manually. Additionally I solved it with mathematica as shown in the picture.Best Chris
Posted 8 years ago
Posted 8 years ago
 Consider that the function has a zero, and that any "rearrangement" that expresses the same function must also exhibit this zero. If, in the new expression, x does not appear in the numerator, then the only way for the function to provide the zero, at least as a limit, is for the denominator to go to infinity. But the only way to do that with finite values for x is for a term of the denominator to itself be rational and to contain x in its denominator.But this is not really different from the clearly unwanted solution where num/denom is rewritten as 1/(num^-1 denom), which is trivial and I think misses the point.
Posted 8 years ago
 Hi Okkes,thanks for looking at it and the manipulations. As you said - there is still the variable in the numerator ... For the spacing: I adjusted the previous file in order to be clearer.Any further ideas or how can I check if it is even possible (or if I am wasting my time ...)Best Chris
Posted 8 years ago
 you forgot to put space between some variable.. I tried it didnot work. Attachments: