丨3丨=3.丨y丨=5.且丨x-y丨=丨x丨+丨y丨.求2x-y的值
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解决时间 2021-11-14 09:56
- 提问者网友：相思似海深
- 2021-11-13 15:22
丨3丨=3.丨y丨=5.且丨x-y丨=丨x丨+丨y丨.求2x-y的值
最佳答案
- 五星知识达人网友：孤老序
- 2021-11-13 15:35
|x|=3 => x=3 or -3
|y|=5 => y=5 or -5
case 1: x=3, y=5
|x-y| = 2
|x|+|y|= 8≠|x-y|
case 2: x=3, y=-5
|x-y| = 8
|x|+|y|= 8=|x-y|
case 3: x=-3, y=5
|x-y| = 8
|x|+|y|= 8=|x-y|
case 4: x=-3, y=-5
|x-y| = 2
|x|+|y|= 8≠|x-y|
when (x,y)= (3,-5)
2x-y= 6+5 =11
when (x,y)= (-3,5)
2x-y= -6-5 =-11
ie
2x-y = 11 or -11
|y|=5 => y=5 or -5
case 1: x=3, y=5
|x-y| = 2
|x|+|y|= 8≠|x-y|
case 2: x=3, y=-5
|x-y| = 8
|x|+|y|= 8=|x-y|
case 3: x=-3, y=5
|x-y| = 8
|x|+|y|= 8=|x-y|
case 4: x=-3, y=-5
|x-y| = 2
|x|+|y|= 8≠|x-y|
when (x,y)= (3,-5)
2x-y= 6+5 =11
when (x,y)= (-3,5)
2x-y= -6-5 =-11
ie
2x-y = 11 or -11
全部回答
- 1楼网友：西风乍起
- 2021-11-13 16:19
x，y是异号，x=5/3，y=-5/3 2x-y=5
或者-5
或者-5
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