已知(x+y)^2-2x-2y+1=0,求2x^2+2xy+3y^2-2x-3y
问题描述：
已知(x+y)^2-2x-2y+1=0,求2x^2+2xy+3y^2-2x-3y
答
(x+y)^2-2x-2y+1=0
(x+y)^2-2(x+y)+1=0
x+y=1
2x^2+2xy+3y^2-2x-3y
=X²+2xy+y²+x²+2y²-2x-3y
=1+x²+2y²-1-y
=x²+y²+2xy-2xy-y+y²
=1-2y(x+y)+yV
=1-2y+y²
=（y-1）²
=任意值了
你看看题有没有错
楼下还改题
哎！
答
(x+y)^2-2x-2y+1=0
(X+Y-1)^2=0
X+Y=1
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答
题目应是 已知(x+y)^2-2x-2y+1=0,求2x^2+5xy+3y^2-2x-3y已知(x+y)^2-2x-2y+1=0,(x+y)^2-2(x+y)+1=0(x+y-1)^2=0x+y-1=0x+y=12x^2+5xy+3y^2-2x-3y=2（x^2+2xy+y^2）+xy+y^2-2x-3y=2(x+y)^2+(x+y)y-2x-3y=2+y-2x-3y=2-2...