(5x + 6)(5x – 6)

This is a difference of squares, so we can simplify using the formula:

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

In this case, let a = 5x and b = 6:

(5x + 6)(5x - 6) = (5x)^2 - (6)^2

= 25x^2 - 36

So the simplified expression is:

25x^2 - 36