14: =x^3-3x^2+3x-1-1
=(x-1)^3-1
=(x-1-1)(x^2-2x+1+x-1+1)
=(x-2)(x^2-x+1)
15: =x^3+x^2-4x^2-4x+7x+7
=(x+1)(x^2-4x+7)
16: =2x^3-x^2-2x^2+x+2x-1
=(2x-1)(x^2-x+1)
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