Question

Find the number of ordered pairs $(m,n)$ of integers that satisfy
\[mn = 2m + 4n.\]

Answer 1

Explanation:

I could only find 4

m n

5 10

6 6

8 4

12 8

I wouldn't know how to find the 5th one if there is such a thing.

I did this with a computer language (delphi). There is no proof that I can think of.