设(x+y)(x-2+y)=35,求x+y的值

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设(x+y)(x-2+y)=35,求x+y的值
设(x+y)(x-2+y)=35,求x+y的值

设(x+y)(x-2+y)=35,求x+y的值
(x+y)(x-2+y)=35
(x+y)(x+y-2)=35
(x+y)^2-2(x+y)-35=0
(x+y-7)(x+y+5)=0
所以:
x+y=7或者
x+y=-5

(x+y)(x-2+y)=35;
(x+y)²-2(x+y)-35=0;
(x+y-7)(x+y+5)=0;
x+y=7或x+y=-5;

(x+y)(x-2+y)=35
(x+y)²-2(x+y)-35=0
(x+y+5)(x+y-7)=0
x+y=-5或x+y=7

(x+y)(x-2+y)=35
(x+y)^2-2(x+y)-35=0
(x+y-7)(x+y+5)=0
x+y=7或x+y=-5

x+y=7,把x+y看成一个整体可用t替换,即t.(t-2)=35

设x+y=t
则:t(t-2)=35
之后就会做了吧~~

x+y=7 (-5)