The expression "|a|" represents the absolute value of the variable "a." In mathematical notation, it is often written as:
|a| = {
a, if a > 0
-a, if a < 0
}
In other words, if "a" is greater than 0 (a > 0), then the absolute value of "a" is equal to "a" itself. If "a" is less than 0 (a < 0), then the absolute value of "a" is equal to the negation of "a," which is "-a."
For example:
If a = 5, then |a| = 5 (because 5 is greater than 0).
If a = -3, then |a| = 3 (because the absolute value of -3 is 3).