Question

1+x-x3-x4>0 x3-2x2+3〈0

Answer 1

1+x-x3-x4>0
(1+x)-x^3(1+x)>0
(1+x)(1-x^3)>0
(1+x)(1-x)(1+x+x^2)>0
因为：x^2+x+1=(x+1/2)^2+3/4>0
所以,(1+x)(1-x)>0
解得：x>1或者x