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The factor theorem says that, if f(a) = 0 in which f(x) represents a polynomial in x, then (x - a) is one of the factors of f(x).
For example, let f(x) = 2x2 - 8. Because f(2) = 2(2)2 - 8 = 0, (x - 2) must be one of its factors. Actually, f(x) = 2x2 - 8 = 2(x + 2)(x - 2).
