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If sum of n terms of a sequence is Sn th...

If sum of n terms of a sequence is `S_n` then its nth term `t_n=S_n-S_(n-1)`. This relation is valid for all `ngt-1` provided `S_0= 0.` But if `S_1=0`, then the relation is valid only for `nge2` and in hat cast `t_1` can be obtained by the relation`t_1=S_1.` Also if nth term of a sequence `t_1=S_n-S_(n-1)` then sum of n term of the sequence can be obtained by putting `n=1,2,3,.n` and adding them. Thus `sum_(n=1)^n t_n=S_n-S_0.` if `S_0=0, then sum_(n=1)^n t_n=S_n.` On the basis of above information answer the following questions: If the sum of n terms of a sequence is `10n^2+7n` then the sequence is (A) an A.P. having common difference 20 (B) an A.P. having common difference 7 (C) an A.P. having common difference 27 (D) not an A.P.

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