`red'
-----

red(RAT)
     :: RAT 񕪂.

RETURN
     L
RAT
     L

   * Asir ͗L̖񕪂ɎIɍs. , LɂĂ͒
     ͍s, 񕪂̓[U[w肵ȂsȂ. ̖񕪂s
     R}h red ł.
   * EZGCD ɂ RAT ̕q, 񕪂.
   * o͂L̑̕, eW GCD  1 ̐W
     ł. qɂĂ͐WƂȂƂ͌Ȃ.
   * GCD ͑ϏdZȂ̂, ̕@ŏ鋤ʈq͉\Ȍ菜
     ̂]܂. ܂, , q傫ȂĂ̂̔̌
     яo, ɎԂ|ꍇ. LZsꍇ, 
     xpɂ, 񕪂sKv.

     [0] (x^3-1)/(x-1);
     (x^3-1)/(x-1)
     [1] red((x^3-1)/(x-1));
     x^2+x+1
     [2] red((x^3+y^3+z^3-3*x*y*z)/(x+y+z));
     x^2+(-y-z)*x+y^2-z*y+z^2
     [3] red((3*x*y)/(12*x^2+21*y^3*x));
     (y)/(4*x+7*y^3)
     [4] red((3/4*x^2+5/6*x)/(2*y*x+4/3*x));
     (9/8*x+5/4)/(3*y+2)

Q
     `nm', `dn', `gcd', `ptozp'

