f(x) = x^5-5x^4+7x^3-2x^2+4x-8 = (x-2)^3(x^2+x+1)f'(x) = 5x^4-20x^3+21x^2-4x+4 = (x-2)^2(5x^2+1)故 f(x) 的 重因式是 (x-2)^3, 三重根是 2.
