Compute |U(4)|, |U(10)|, |U(40)|
I know that I have to compute the order of the group for each. Am I looking for |U(4)|=2, |U(10)|=4 and |U(40)|=10? as the answer?
Thanks in advance
When ever you find the order of (same as ), we are always guaranteed to have 1 and n-1 in , so when .
In your case,
, so .
, so .
, so .
So two of your answers were correct.
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As an aside (if you see something like this in the future): If is a prime, then