第1个回答 2013-10-12
解:由题意得
|X-Y+3|+|X+Y-1999|=0
∴X-Y+3=0,X+Y-1999=0
解得X=998,Y=1001
当X=998,Y=1001时
(X-Y)/(X+2Y)
=(998-1001)/(998+2×1001)
=-3/3000
=-1/1000
第2个回答 2013-10-12
解:|X-Y+3|和|X+Y-1999|互为相反数,|X-Y+3|≥0,|X+Y-1999|≥0∴X-Y+3=0,X+Y-1999=0解得:X=998,Y=1001 X+2Y分之X-Y=(X-Y)/(X+2Y)=(998-1001)/(998+2*1001)=-3/3000=-1/1000
第3个回答 2013-10-12
两个绝对值要互为相反数则都为0!那么有X-Y=-3然后X+Y=1999所以X+Y+2=2001