Question 469066
(A+C)(A+D)(B+C)(B+D) 
=((A+C)(A+D))((B+C)(B+D)) ASSUMING associativity

= (A + CD)(B + CD) from A+BC=(A+B)(A+C)

= (CD + A)(CD + B) from A+B=B+A

= CD + AB from  A+BC=(A+B)(A+C)