Michael A. answered 02/13/17
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x8 - 1 = (x4 + 1)(x4 - 1) = (x4 + 1)(x2 + 1)(x² - 1) = (x4 + 1)(x2 + 1)(x + 1)(x - 1)
This is good practice with the difference of two squares.
Remember, a² - b² = (a + b)(a - b)