Factor Completely Four Terms by Factoring by Grouping: ab-3a+5b-15

The following four terms need to be factored completely: ab-3a+5b-15. Initially it is checked that all four terms do not have a greatest common factor (GCF). Then the four terms are factored by grouping. In this method the GCF is factored out of the first two terms and then the last two terms. If the remaining binomial from each set of terms is identical, then this is a common binomial factor that is then factored out.