分解因式x3-9x+8

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分解因式x3-9x+8
分解因式x3-9x+8

分解因式x3-9x+8
x3-x-8x+8
=(x3-x)+(8-8x)
x(x+1)(x-1)-8(x-1)
=(x-1)(x2+x-8)

x(x+3)(x-3)+8

x³-9x+8
=x³-x-8x+8
=x(x²-1)-8(x-1)
=x(x+1)(x-1)-8(x-1)
=(x-1)(x²+x-8)
=(x-1)[(x+(1+√33)/2][x+(1-√33)/2]
不是到(x-1)(x²+x-8)就结束了,实数范围内分解应该到(x-1)[(x+(1+√33)/2][X+(1-√33)/2]

x³-9x+8
=x³-1-9x+9
=(x-1)(x²+x+1)-9(x-1)
=(x-1)(x²+x+1-9)
=(x-1)(x²+x-8)