What is the general pattern when you divide each polynomial (x^3-Y^3, x^5-y^5, x^7-y^7, x^9-y^9) by x-y?
do some long divsions
(x^3 - y^3)/(x-y) = x^2 + xy + y^2
(x^5-y^5).(x-y) = x^4 + yx^3 + y^2 x^2 + y^3 x +y^4
mmmhhh
(x^n - y^n)/(x-y) = x^(n-1) + y x^(n-2) + y^2 x^(n-3) + ... + y^(n-2) x + y^(n-1)