问题
选择题
若2x2-2xy+y2-4x+4=0,那么x-y的值是( )
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答案
∵2x2-2xy+y2-4x+4=0,
∴x2-2xy+y2+x2-4x+4=0,
∴(x-y)2+(x-2)2=0,
∴
,x-y=0 x-2=0
解得
.x=2 y=2
∴原式=2-2=
.1 4
故选A.
若2x2-2xy+y2-4x+4=0,那么x-y的值是( )
|
∵2x2-2xy+y2-4x+4=0,
∴x2-2xy+y2+x2-4x+4=0,
∴(x-y)2+(x-2)2=0,
∴
,x-y=0 x-2=0
解得
.x=2 y=2
∴原式=2-2=
.1 4
故选A.