已知x²－5x－2＝0
x^2-5x=2
x－2分之（x－2）³－（x-1）²＋1
=[(x-2)^3-(x-1)^2+1]/(x-2)
={(x-2)^3-[(x-1)^2-1]}/(x-2)
={(x-2)^3-[(x-1-1)(x-1+1)]}/(x-2)
={(x-2)^3-[(x-2)x]}/(x-2)
=(x-2)[(x-2)^2-x]/(x-2)
=(x-2)^2-x
=x^2-5x+4
=2+4
=6