[" 7.If Sn denotes the sum of "n" terms of an AP whose common difference is "d" and first term is a,find "],[S_(n)-2S_(n-1)+S_(n-2)" ."]

If S_(n) denotes the sum of n terms of an A.P. whose common difference is d and first term is a,find S_(n)-2S_(n-1)+S_(n-2)

If S_n denotes the sum of n terms of an A.P. whose common difference is d and first term is a, find S_n-2S_(n-1)+S_(n-2)

If S_(n) denotes the sum of n terms of an AP whose common difference is d, the value of S_(n)-2S_(n-1)+S_(n-2) is

If S_(n) denote the sum to n terms of an A.P. whose first term is a and common differnece is d , then S_(n) - 2S_(n-1) + S_(n-2) is equal to

If S_n denotes the sum of n terms of an A.P. whose first term is a, and the common difference is d Find: = Sn - 2Sn + S(n +2) .

Let S_(n) denotes the sum to terms of an A.P. whose first term is a . If the commom difference d is given by d = S_(n) - kS_(n-1) + S_(n-2) , then k is equal to

Let S_n denote the sum of n terms of an AP whose first term is a. If common difference d is given by d=Sn-kS_(n-1)+S_(n-2) , then k is :