inequality 10分

First of all, the roots of x ( x - 5) (x + 1) = 0 are x = -1, 0 and 5.
Then we can list out the range of x in table form as follows:

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Apr08/Crazyineq1.jpg

So, for x ( x - 5) (x + 1) > 0, we have -1 < x < 0 or x > 5
For x ( x - 5) (x + 1) < 0, we have x < -1 or 0 < x < 5
(用了正負數相乘的結果)