find the factor

mn-4m-5n+20

To find the factors of the expression mn - 4m - 5n + 20, we can use a method called grouping.

First, let's group the terms together: (mn - 4m) - (5n - 20).

Now, let's factor out the common factors from each grouping:

mn - 4m can be factored as m(n - 4).

5n - 20 can be factored as 5(n - 4).

Now, we have: m(n - 4) - 5(n - 4).

Notice that (n - 4) is common to both terms. We can factor it out:

(n - 4)(m - 5).

Therefore, the factors of the expression mn - 4m - 5n + 20 are (n - 4)(m - 5).