How do i express 1/2 of the difference of a number cubed and one?

1/2(x^3-1) is how you would express 1/2 of the difference of a number cubed and one. Putting 1/2 on the outside of the parentheses multiply all number inside of the parentheses by 1/2. X^3 represents an unknown number, cubed. The difference of a number cubes and one is x^3-1.