First, since it makes the negative a positive, b must be negative.
Then, since the end result is less than a, we can write
ab < |a|
From this, we get two equations
1. ab2. ab>-a
1.
abb<1
2.
ab>-a
b>-1
So, b is in-between -1 and 1, but since we’ve determined that is negative, -1
