Prove for every natural number n, x-y divides (x^n) - (y^n)
This is another proof by induction, so first we prove the first case, which for the natural numbers is 1.
x - y divides (x^1) - (y^1) = 1(x-y) so this is true.
Now by induction we must show that x-y divides x^(n+1) - y^(n+1)
x^(n+1) - y^(n+1)
= x(x^n) - y(y^n)
= x(x^n) - y(x^n) + y(x^n) - y(y^n)
= (x-y)(x^n) + y(x^n - y^n)
so now we have a form where x-y divides the first term (since x-y is a factor) and divides the second term((x^n - y^n)) by the hypothesis of induction.
Thus x-y divides (x^n) - (y^n) for all natural numbers n.
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