若X,Y满足3(XX+YY+ZZ)=(X+Y+Z)(X+Y+Z),则X=Y=Z.请说明理由.

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/17 01:19:02
若X,Y满足3(XX+YY+ZZ)=(X+Y+Z)(X+Y+Z),则X=Y=Z.请说明理由.

若X,Y满足3(XX+YY+ZZ)=(X+Y+Z)(X+Y+Z),则X=Y=Z.请说明理由.
若X,Y满足3(XX+YY+ZZ)=(X+Y+Z)(X+Y+Z),则X=Y=Z.请说明理由.

若X,Y满足3(XX+YY+ZZ)=(X+Y+Z)(X+Y+Z),则X=Y=Z.请说明理由.
3(X²+Y²+Z²)=X²+Y²+Z²+2XZ+2XY+2ZY
(X²+Y²+Z²)+ 2(X²+Y²+Z²)=2(XZ+XY+ZY)+(X²+Y²+Z²)
XX+YY+ZZ=XZ+XY+ZY
∴XX=XZ →X=Z
YY=XY →X=Y
ZZ=ZY →Z=Y
∴X=Y=Z

证明:(X+Y+Z)(X+Y+Z)=XX+YY+ZZ+2XY+2YZ+2XZ,代入得
3(XX+YY+ZZ)=XX+YY+ZZ+2XY+2YZ+2XZ,移项得
2XX+2YY+2ZZ-2XY-2YZ-2XZ=0
即(X-Y)^2+(Y-Z)^2+(X-Z)^2=0,
所以(X-Y)=(Y-Z)=(X-Z)=0。
所以X=Y=Z