The absolute value is the positive magnitude of a particular number or variable and is indicated by two vertical lines: \(\left|-5\right| = 5\). In the case of a variable absolute value (\(\left|a\right| = 5\)) the value of a can be either positive or negative (a = -5 or a = 5).
If \( \left|a + 9\right| \) - 1 = 9, which of these is a possible value for a?
| -2 | |
| 1 | |
| -13 | |
| -1 |