Respuesta :

Answer:

(a - 2b - 3c)(a - 2b + 3c)

Step-by-step explanation:

a² + 4b² - 4ab - 9c²

= (a - 2b)² - 9c² ← difference of squares which factors in general as

a² - b² = (a - b)(a + b) , then

(a - 2b)² - 9c²

= (a - 2b)² - (3c)²

= (a - 2b - 3c)(a - 2b + 3c)