若x2+y2?x+4y+17/4=0,求(2x+y)(2x-y)-(2x-y)2的值.
若
x2+y2?x+4y+=0,求(2x+y)(2x-y)-(2x-y)
2的值.
優(yōu)質(zhì)解答
∵x
2+y
2-x+4y+
=0,
∴(x-
)
2+(y+2)
2=0,
∴x=
,y=-2,
∵原式=4x
2-y
2-(4x
2-4xy+y
2)=4xy-2y
2,
∴當(dāng)x=
,y=-2時,原式=4×
×(-2)-2×(-2)
2=-12.
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