Step-by-step explanation:
I just answered this.
I cannot draw here.
but it will mark all dots, where row number = column number.
and all dots, where row number + column number = 8.
this will create a giant X.
the 2 lines go from (0, 8) to (8, 0), and from (0, 0) to (8, 8) with (4, 4) being the central intersection point.