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已知x+y-z=-1,x²+y²-z²=-11,那么﹙2x-y²+2y﹚-﹙x²-z²﹢2z﹚=?
人气:163 ℃ 时间:2020-01-31 21:17:30
解答
x²+y²-z²=-11
y²=-x²+z²-11
﹙2x-y²+2y﹚-﹙x²-z²﹢2z﹚
=2x+x²-z²+11+2y-x²+z²-2z
=2x+2y-2x
=2(x+y-z)
=-2
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