x²+y²-4x+y+17/4=0 ,求(x+y)的值

即(x²-4x+4)+(y²+y+1/4)=0
(x-2)²+(y+1/2)²=0
所以x-2=y+1/2=0
x=2,y=-1/2
所以x+y=3/2

x²+y²-4x+y+17/4=0
(x-2)²+(y+1/2)²=0

x-2=0
y+1/2=0
x=2
y=-1/2

x+y
=2-1/2
=3/2

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x²+y²-4x+y+17/4=0
x²-4x+4+(y²+y+1/4)=0
(x-2）²+（y+1/2）²=0
因为有理数的平方大于等于0，而(x-2）²+（y+1/4）²=0
所以x-2=0，y+1/2=0
x=2,y=-1/2
X+y=2-1/2=3/2