（m\m+n）+（m\m-n）-(n＠\m＠-n＠）=m(m-n)/(m+n)(m-n)+m(m+n)/(m+n)(m-n)-n^2/(m+n)(m-n)=(m^2-mn+m^2+mn-n^2)/(m+n)(m-n)=(2m^2-n^2)/(m^2-n^2) m\n=5\3 so 3n=5m 设n=5k 那么 m=3k(2m^2-n^2)/(m^2-n^2) =（2*9k^...