# Coprime Integers/Examples/-9 and 16

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## Example of Coprime Integers

$-9$ and $16$ are coprime.

## Proof

The positive divisors of $-9$ are $1$, $3$ and $9$.

The positive divisors of $16$ are $1$, $2$, $4$, $8$ and $16$.

The only integer in common between them is $1$.

Hence the result by definition of coprime.

$\blacksquare$

## Sources

- 1980: David M. Burton:
*Elementary Number Theory*(revised ed.) ... (previous) ... (next): Chapter $2$: Divisibility Theory in the Integers: $2.2$ The Greatest Common Divisor