2loga（M-N）=loga（m)+log(N),
loga(M-N)^2=loga(M*N)
(M-N)^2=M*N
M^2-2MN+N^2=MN
M^2-3MN+N^2=0
M=(3±√5)/2N
N/M=2/(3±√5)
=2(3±√5)/(6-5)
=2(3±√5)
因为M-N>0 M>0 N>0
M>N
所以0