If Sn, denote the sum of n terms of an A.P. with first term a and common difference d such that , is independent of x, then

Given AP in which First term = a, Common difference = d, Number of terms = n


And Sn denotes the sum of n terms


So



and


Now,






If d= 2a


Sx /Skx = (2×a) / (k2×2a)


= 1/ k2


So Sx /Skx is independent of if d = 2a

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