解:4x+y=5 (1)3x+2y=4 (2)(1)-(2)得:4x+y-(3x+2y)=5-44x-3x+y-2y=1x-y=1
4x+y-(3x+2y)=x-y=5-4=1
4x+y=5 A3x+2y=4 BA-B=X-Y=1