∵丨m-n-4丨≥0,（mn+1）²≥0又丨m-n-4丨+（mn+1）²=0∴丨m-n-4丨=0,（mn+1）²=0∴m-n-4=0,mn+1=0∴m-n=4 ①,mn= -1②,把（-2mn+2m+3n）-（3mn+2n-2m）-（m+4n+mn）的括号去掉,并且合并同类项,此式可...