Question 35602
To find the common difference, just subtract any two consecutive numbers.  If it is an arithmetic sequence, it MUST be the same no matter which two you subtract.   


In this case take {{{1/6 - 1/2}}}, which is {{{1/6 - 3/6=-2/6 = -1/3}}}


Any other two consecutive numbers in which you subtract any number minus the previous number should get you the same result.


R^2 at SCC