If m|n, Then (a^m - b^m)|(a^n - b^n)

Let's first talk about the case when \(m=1\) and \(n=1\), then this case is trivial:

$$ (a-b)|(a-b) $$

Now let \(m=1\) and \(n \gt 1\). We are going to prove by using mathematical induction that:

$$ (a-b)|(a^n - b^n) $$

We know that there exists a value of \(k\) (=1) for which \((a-b)|(a^k - b^k)\). If we use \(k+1\):

$$ a^{k+1} - b^{k+1} = a(a^k - b^k) + b^k (a-b) $$

This means if \((a-b) | a(a^k - b^k)\) and \((a-b) | b^k (a-b)\), then \((a-b)|(a^{k+1} - b^{k+1})\). This proves that \((a-b)|(a^n - b^n)\) when \(n \gt 1\). Now let's talk about the next case where \(m \gt 1\), \(n \gt 1\) and \(m|n\), and let \(mk=n\), then:

$$ a^n - b^n = a^{mk} - b^{mk} = (a^m)^k - (b^m)^k $$

Let \(x = a^m\) and \(y = b^m\):

$$ a^n - b^n = x^k - y^k $$

Through the previous case, we know that \(x-y\) divides \(x^k - y^k\), which means:

$$ (x-y)|(a^n - b^n) $$$$ (a^m - b^m)|(a^n - b^n) $$

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