若X+2Y+3Z=10.4X+3Y+2Z=15,求X+Y+Z的值

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若X+2Y+3Z=10.4X+3Y+2Z=15,求X+Y+Z的值若X+2Y+3Z=10.4X+3Y+2Z=15,求X+Y+Z的值若X+2Y+3Z=10.4X+3Y+2Z=15,求X+Y+Z的值X+2Y

若X+2Y+3Z=10.4X+3Y+2Z=15,求X+Y+Z的值
若X+2Y+3Z=10.4X+3Y+2Z=15,求X+Y+Z的值

若X+2Y+3Z=10.4X+3Y+2Z=15,求X+Y+Z的值
X+2Y+3Z=10
4X+3Y+2Z=15
两式相加
5X+5Y+5Z=25
5(X+Y+Z)=25
X+Y+Z=5

难呢!

5
两个公式相加

abcdefghijklmnopqrstuvwxyz

设X+Y+Z=A,则
X+2Y+3Z=10 (1)
3X+2Y+Z=10=10-A (2)

(1)+(2)。得
4A=20-A
A=5
所以X+Y+Z=5

可以设:
X+Y+Z=a(X+2Y+3Z)+b(4X+3Y+2Z)
展开各项相等就有:

a+4b=1,2a+3b=1,3a+2b=1,
可以得到a=1/5,b=4/5,
既有X+Y+Z=10/5+15*4/5=14,