题干
已知
=
=
，求
．
| x |
| 2 |
| y |
| 3 |
| z |
| 4 |
| 2 |
| x |
| + |
| 2 |
| y |
| + |
| z |
| 3 |
| y |
| - |
| z |
答案(点此获取答案解析）
解：令
=
=
| x |
| 2 |
| y |
| 3 |
