Answer:
(ab + cd + ac - bd)(ab + cd - ac + bd)
Step-by-step explanation:
(ab + cd)² - (ac - bd)² ← is a difference of squares and factors in general as
a² - b² = (a + b)(a - b)
Here a = ab + cd and b = ac - bd , then
= (ab + cd + ac - bd)(ab + cd - (ac - bd))
= (ab + cd + ac - bd)(ab + cd - ac + bd)
