1
-1
-2
2
Given A.P is 1/3q, 1-6/3q, 1-12/3q
Then, 1/3q, 1/3q - 2, 1/3q - 4 will also be in AP.
Which results in, 1/3q, 1/3q - 2, 1/3q - 4
It can be seen clearly that the series is decreasing by the quantity (2)
Hence, the common difference is -2