(1) (x+1)(x-5)>0 x>5或x<-1 集合{x|x>5或x<-1} 区间是(负无穷,-1)(5,正无穷)
(2) (x-1)(x+5)<0 -5
(1)( x+ 1)(x-5)>0 x<-1或x>5
{x|x<-1或x>5} (-∞,-1)和(5,+∞)
(2) (x-1)(x+5)<0 -5
{x| -1< x<-1/2} (-1,-1/2)
(4) 3x-2x^2-1<0 2x^2-3x+1>0 ( 2x-1)(x-1)>0 x<1/2或x>1
{x|x<1/2或x>1 } (-∞,1/2)和(1,+∞)