March 2009
Step 1 — Solution
The first row starts with the number 4. The starting number of any other row is 3 steps on from that of the previous one. This tells us that the first number in row m is of the form
The difference between successive numbers in the first row is 3, and the difference between successive numbers in any other row is 2 greater than the difference in the previous row. This means that the difference between successive numbers in row m is
The nth entry in row m is equal to the first entry plus (n-1) times the difference in that row, so the nth entry in row m is