x^3-[x^2-x+1]=x^3-x^2+x-1=x^3+x-(x^2+1)=(x^2+1)(x-1)
x^2+1>0
当x-1>0,即x>1时,x^3-[x^2-x+1]>0,即 x^3>x^2-x+1
当x-1=0,即x=1时,x^3-[x^2-x+1]=0,即 x^3=x^2-x+1
当x-1