(x-1)的立方-3=3/8
(x-1)的立方-3+3=3/8+3
(x-1)的立方=27/8
(x-1)的立方=(3/2)的立方
两边开立方:
x-1=3/2
x=3/2+1
x=5/2,【x=2.5】