x³-11x²+31x-21x³-4xy²-2x²y+8y过程详细点

Question

x³-11x²+31x-21
x³-4xy²-2x²y+8y过程详细点

Answer 1

x³-11x²+31x-21
=x³-1-(11x²-31x+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)
最后是y³
x³-4xy²-2x²y+8y
=x(x²-4y²)-2y(x²-4y²)
=(x-2y)(x²-4y²)
=(x-2y)(x+2y)(x-2y)
=(x+2y)(x-2y)²