Question

如果|x+2y+1|+2x-y-5|=0,则x+y的值为？

如果|x+2y+1|+|2x-y-5|=0,则x+y的值为？

Answer 1

绝对值项恒非负，两绝对值项之和=0，两绝对值项分别=0
x+2y+1=0 (1)
2x-y-5=0 (2)
(1)+(2)×2
5x-9=0
x=9/5
(1)×2-(2)
5y+7=0
y=-7/5

x+y=9/5+(-7/5)=2/5

Answer 2

|x+2y+1|+2x-y-5|=0,

所以x+2y+1=0
2x-y-5=0,
解得x=9/5,y=-7/5
x+y=2/5

Answer 3

2x-y-5|左边是不是少了一杠 |x+2y+1|+2x-y-5|=0,

所以x+2y+1=0
2x-y-5=0,
解得x=9/5,y=-7/5
x+y=2/5

Answer 4

绝对值大于等于0，相加等于0，若有一个大于0，则另一个小于0，不成立。所以两个都等于0‘所以x-2y+1=0,(1) 2x-y-5=0 (2) (2)×2-(1) 4x

Answer 5

|x+2y+1|+2x-y-5|=0,

则
x+2y+1=0 (x+y)+y=-1 (1)
2x-y-5=0, 2(x+y)-3y=5 (2)
(1)*3+2
5(x+y)=2
x+y=2/5

Answer 6

X=11/3;y=7/3.x+y=18/3=6