3m=5+2(m-1)3m=5+2m-2m=3代入m-n=13-n=1n=2代入3m-2n=59-4=5,成立所以m=3,n=2
3m=5+2(m-1)3m=5+2m-23m=2m+3所以m=3代入m-n=1得n=2
