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已知3x-4y-z=02x+y-8z=0,求x2+y2-z2xy+yz的值.
题目详情
已知3x-4y-z=0 2x+y-8z=0,求
的值.
x2+y2-z2 |
xy+yz |
▼优质解答
答案和解析
∵由题意得,
,解得
,
∴原式=
=
=
.
|
|
∴原式=
9z2+4z2-z2 |
3z•2z+2z•z |
12z2 |
8z2 |
3 |
2 |
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