(3-x)/(1+x)>=x求解

当x+1>0，即x>-1时
3-x>=x(x+1)
x^2+2x-3<=0
(x+3)(x-1)<=0
-3<=x<=1
即-1<x<=1

当x+1<0,即x<-1时
3-x<=x(x+1)
x^2+2x-3>=0
(x+3)(x-1)>=0
x<=-3或x>=1
即x<=-3

综上可得，(3-x)/(1+x)>=x的解集为：

{x|-1<x<=1}∪{x|x<=-3}

(3-x)/(1+x)>=x
3-x>=x+x^2
3>=x^2+2x
x^2+2x-3<=0
(x+3)(x-1)<=0
-3<=x<=1

X=1 或-3