8x^3 + 1728

Factor out 8

8(x^3 + 216)

Now, this is in the form of the sum of two cubes,
(a^3 + b^3) = (a + b)(a^2 - ab + b^2)

Hint, a^3 = x^3, a = x
And, b^3 = 216, b = 6
8(x^3 + 216)

Now, you should be able to easily factor this.