Task. Factorize this sum:
(x+y)(2x+3y)−(x+y)(x+1)
Solution. We should represent this expression as a product. Notice that (x+y) is the common factor of both summands, so
(x+y)(2x+3y)−(x+y)(x+1) =(x+y)\Big{(}(2x+3y)-(x+1)\Big{)}
=(x+y)(2x+3y−x−1)
=(x+y)(x+3y−1).
Answer.
(x+y)(2x+3y)−(x+y)(x+1)=(x+y)(x+3y−1).