Some may be harder than the previous ones. If the algebraic exercises are not understandable, try them later. Observe the sum of 2 and 3 is five.
Factorization is done.
So they can be put in and pulled out of products at convenience. This can be justified via deductive chains of reasons depending on two properties of multiplication - the associative law and the commutative law. This suggests that when the value of the original expression is requested, no computation is needed. The value will be zero. Of course, some computation would be needed if the simplification had not been done.