`nm', `dn'
----------

nm(RAT)
     :: RAT ̕q.
dn(RAT)
     :: RAT ̕.

RETURN
     ܂͑
RAT
     L܂͗L

   * ^ꂽL܂L̕qyѕԂ.
   * L̏ꍇ, ͏ɐ, ͕q.
   * L̏ꍇ, Pɕ, qoł. Lɑ΂
     , 񕪂͎Iɂ͍sȂ. `red()'𖾎IɌĂяoKv
     .

     [2] [nm(-43/8),dn(-43/8)];
     [-43,8]
     [3] dn((x*z)/(x*y));
     y*x
     [3] dn(red((x*z)/(x*y)));
     y

Q
     `red'

