Find an integer n > 20 so that the equation 3x = b always have a unigue solution in Zn regardless of the value b
Not to sure what Zn means
Can the value of b be anything?
Please help
By,Originally Posted by mathlg
$\displaystyle \mathbb{Z}_n$ we mean the group of positive integers added modulo $\displaystyle n$.
I believe the theorem goes that,
$\displaystyle ax=b$ has a solution in $\displaystyle \mathbb{Z}_n$ when, $\displaystyle \gcd(b,n)=1$.
For your problem you need to find all the integers relatively prime to $\displaystyle 20$ and less. This is called the 'phi-function'. Thus, you need to find the smalles $\displaystyle n>20$ such as all the previous integers are relatively prime to it. Meaning a prime number, the smallest after 20 is 23.