All intervals are elements of Real Numbers.
Oftentimes you have to write the sign of f(x) according to the intervals.
For example this graph:
The Interval - f(x) sign table looks as such:
| Positive/Negative regions | - | - | - | - |
|---|---|---|---|---|
| Interval | -inf → -2 | -2 ⇒ 1 | 1 → 3 | 3 → inf |
| SIgn of f(x) | - | + | - | + |
Writing Inequalities
X < -5 U x > 3