Re: rationalize numerator of quotient

*To*: mathgroup at smc.vnet.net*Subject*: [mg81160] Re: rationalize numerator of quotient*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Fri, 14 Sep 2007 03:38:02 -0400 (EDT)*References*: <fcb3ok$fjj$1@smc.vnet.net>

Murray Eisenberg wrote: > I have a quotient such as: > > (Sqrt[x] - 2)/(x-4) > > I want to "rationalize the numerator" by multiplying numerator and > denominator each by Sqrt[x] + 2 so as to obtain result: > > 1/(Sqrt[x]+2) > > How? > If you mean doing it automatically for any fraction, then I have no answer for you ... If you would like to do it manually, then try this: expansion[frac_, mul_] := Expand[Numerator[frac] mul]/(Denominator[frac] mul) (What is the operation of multiplying the numerator and denominator by the same factor called in English? I used the name "expansion" here, a literal translation from my mother tongue, but I am sure it is not correct.) expansion[(Sqrt[x] - 2)/(x-4), Sqrt[x]+2] -- Szabolcs