Consider the set of numbers where and are elements of . which in is the same as . Write down all 4 elements of this set of numbers. Which elements have inverses?
Consider the set of numbers where and are elements of . which in is the same as . Write down all 4 elements of this set of numbers. Which elements have inverses?
What do you think the elements of the set are? What numbers are of the form where and are either 1 or 0?
To find out which elements have inverses, square each element and see what happens.