2x立方=-1/4
x立方=-1/8
x=-1/2还有一题 3（x-1)立方-81=0(x+1)立方=83（x-1)立方-81=03（x-1)立方=81（x-1)立方=27x-1=3x=4(x+1)立方=8x+1=2x=1