Factor this expression completely and then place the factors in the proper location on the grid. note: place factors alphabetically in the grid! mn - 4 m - 5 n + 20

First we are going to group the terms that contains the common factor  in one parenthesis, and the other ones in another parenthesis:


Notice that our the terms in our first parenthesis have a common factor , and the terms in our second one have the common factor . Lets factor those out:

Now we have a common factor  in both terms, so we can factor those out as well:


We can conclude that the completely factored expression ordered alphabetically is .