题目内容
若
=
=
，则
=
．
| x |
| 3 |
| y |
| 4 |
| z |
| 5 |
| x+y |
| x-2y+3z |
| 7 |
| 10 |
| 7 |
| 10 |
分析：首先设
=
=
=k，则可得x=3k，y=4k，z=5k，然后代入
，再化简求解即可求得．
| x |
| 3 |
| y |
| 4 |
| z |
| 5 |
| x+y |
| x-2y+3z |
解答：解：设
=
=
=k，
则x=3k，y=4k，z=5k，
则
=
=
．
故答案为：
．
| x |
| 3 |
| y |
| 4 |
| z |
| 5 |
则x=3k，y=4k，z=5k，
则
| x+y |
| x-2y+3z |
| 3k+4k |
| 3k-8k+15k |
| 7 |
| 10 |
故答案为：
| 7 |
| 10 |
点评：此题考查了比例的性质．此题比较简单，注意掌握设
=
=
=k的解题方法是解此题的关键．
| x |
| 3 |
| y |
| 4 |
| z |
| 5 |
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