數學一元一次的解集的問題.....

(x-3)(x+1)>0
So, there will be two cases :
(i) (x-3)>0 & (x+1)>0,
OR
(ii) (x-3)<0 and (x+1)<0
For case (i), to make sure this happens, x must be >3
For case (ii), to make sure this happens, x must be <1
So, the answer for the question should be (x>3) or (x<1)