factor 9b^2-4 as a difference of two squares?

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

9b^2 - 4
= 9b^2 + 6b - 6b - 4
= (9b^2 + 6b) - (6b + 4)
= 3b(3b + 2) - 2(3b + 2)
= (3b + 2)(3b - 2)

(3b)² - 2²
(3b - 2)(3b + 2)

(3b-2)x(3b+2)