若x(x-1)-(x²+y)=3,则2分之x²+y²+xy=?
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若x(x-1)-(x²+y)=3,则2分之x²+y²+xy=?
若x(x-1)-(x²+y)=3,则2分之x²+y²+xy=?
若x(x-1)-(x²+y)=3,则2分之x²+y²+xy=?
x(x-1)-(x²+y)=3
x²-x-x²-y=3
x+y=-3
两边同时平方得
x²+2xy+y²=9
所以2分之x²+y²+xy=1/2(x²+y²+2xy)=9/2
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