(1+x)(2-x)(x2-2x-7)>0解不等式
问题描述:
(1+x)(2-x)(x2-2x-7)>0解不等式
答
(1+x)(2-x)(x2-2x-7)=(1+x)(2-x)(x-1-2√2)(x-1+2√2)=-(x+1)(x-2)(x-1-2√2)(x-1+2√2)=
(1+x)(2-x)(x2-2x-7)(x-1-2√2)(x-1+2√2)>0
等介于(x+1)(x-2)(x-1-2√2)(x-1+2√2)