Next, imagine the number line with these numbers and marked, and the number moving from left to right along the line. When it's right over on the left-hand side, . When it's somewhere in the middle , and when it's going off at the right-hand end, . So, look at the signs of your factors and in each of these three ranges of values of . For instance:
When (e.g. ), is negative and is also negative. And a negative times a negative equals a positive. So is positive. Which is not what we want: we want values of that make .
Now look at the other two ranges: and , and see what happens to the signs in each case.
I hope you can finish it now.