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Start by drawing the first and second squares on your page and copy down their centers coordinates. Write these in a table with the X and Y axis in different collumns, this is so you can look for a pattern afterwards. You will see that the X axis' are increasing by three each time while the Y axis' are increasing by one. Now using this information draw square three onto your grid then add this into your table. You should now see that Y equals the term plus one ( this can be exressed as T+1=Y). You may also be able to see that X is equal to the term times three minus one for posotives or zero or term times three plus one for negative numbers. From this you can work out all sums involving coordinate squares.