x^4+64=X^4+64+16X^2-16X^2=(X^2+8)-16X^2=(X^2+8-4X)(X^2+8+4X) x^3-11x^2+31x-2=(x³-1)-(11x³-31x+20)=(x-1)(x²+x+1)-(11x-20)(x-1)=(x-1)(x²+x+1-11x+20)=(x-1)(x²-10x+21)=(x-1)(x-3)(x-7)
