(x-40)[200-10(x-50)]=2000求简便计算过程,

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(x-40)[200-10(x-50)]=2000求简便计算过程,
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(x-40)[200-10(x-50)]=2000求简便计算过程,
(x-40)[200-10(x-50)]=2000求简便计算过程,

(x-40)[200-10(x-50)]=2000求简便计算过程,
令y=x-40,那么原题变为
y[200-10(y-10)]=2000==>y[20-(y-10)]=200==>-y^2+30y-200=0
==>(y-10)(y-20)=0
因此,y=10或y=20
而x=y+40,得x=50或x=60

(x-40)[200-(10x-500)]=2000
(x-40)[200-10X+500)=2000
(x-40)[700-10X]=2000
(x-40)[70-X]=200
70(x-40)-X(x-40)=200
70x-2800-x2+40x=200
x2-110x+3000=0
求根公式 ,x=50,x=60
注x2,x是平方,不好写,,,