Simplify (2x – 5y)3 – (2x + 5y)3.

The given expression is a difference of cubes, which can be simplified using the formula:

a^3 - b^3 = (a - b)(a^2 + ab + b^2)

Here, a = (2x - 5y) and b = (2x + 5y).

Substitute these values into the formula:

(2x - 5y - 2x - 5y)[(2x - 5y)^2 + (2x - 5y)(2x + 5y) + (2x + 5y)^2]

Simplify the expression inside the first bracket:

-10y

Simplify the expression inside the second bracket:

(4x^2 - 25y^2) + (4x^2 - 25y^2) + (4x^2 + 25y^2)

Combine like terms:

12x^2

So, (2x - 5y)^3 - (2x + 5y)^3 simplifies to -10y * 12x^2, or -120yx^2.