Absolute value is defined as the distance of a number from zero on a number line.
Since, the distance can never be negative, hence, absolute value can never be negative.
For example 1 is 1 away from the origin and -1 is also, 1 away from the origin.
Therefore, absolute value of both -1 and 1 is 1. Mathematically, we can write
|-1| =1
|1|=1
Therefore, the number 1 and -1 on the number line have an absolute value of 1.