5m-3n＜0
则,5m-3n-10
2-5m+3n>2
|2-5m+3n|=2-5m+3n
|5m-3n-1|-|2-5m+3n|
=-(5m-3n-1)-(2-5m+3n)
=-5m+3n+1-2+5m-3n
=-1