Write an equation that can be used to find d, the difference between the last number and the first number, for any row r.

Question

row 1. 1

row 2. 4. 7

row 3. 10. 13. 16

row 4. 19. 22. 25. 28

Answer 1

It is quite simple.

Please see each row and the relation between row.

The answer is (r-1)*3 .