若(x+y)(1-x-y)+6=0,则x+y的值是_____

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若(x+y)(1-x-y)+6=0,则x+y的值是_____若(x+y)(1-x-y)+6=0,则x+y的值是_____若(x+y)(1-x-y)+6=0,则x+y的值是_____若(x+y)(1-x

若(x+y)(1-x-y)+6=0,则x+y的值是_____
若(x+y)(1-x-y)+6=0,则x+y的值是_____

若(x+y)(1-x-y)+6=0,则x+y的值是_____
若(x+y)(1-x-y)+6=0,
-(x+y)²+(x+y)+6=0;
(x+y)²-(x+y)-6=0;
(x+y-3)(x+y+2)=0;
x+y=3或x+y=-2;
则x+y的值是____3或-2_
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若(x+y)(1-x-y)+6=0
(x+y)[1-(x+y)]+6=0
(x+y)-(x+y)^2+6=0
(x+y)^2-(x+y)-6=0
[(x+y)-3][(x+y)+2]=0
x+y-3=0 x+y+2=0
x+y=3 或 x+y=-2

(x+y)(1-x-y)+6=0
(x+y)[1-(x+y)]+6=0
(x+y)-(x+y)²+6=0
(x+y-1/2)²=25/4
x+y-1/2=±√(25/4)=±5/2
∴x+y=-2或者x+y=3

答案是3或-2

令x-y=a,则a*(1-a)+6=0
a²-a-6=0,
(a-3)(a+2)=0,
解得a=3或者a=-2
即x+y=3或-2