Im assuming this is real numbers?

If a number has modulus less than or equal to 1, then that quantity must be between -1 and 1.

If a number is between -1 and 1, then it is both greater than -1 and at the same time less than +1. The set of numbers between -1 and 1 is the intersection of two sets: all numbers greater than -1 intersected with all numbers less than +1.

So at the end you need to find the intersection of the two sets because you are trying to keep the expression in the modulus between two values.