Find the sum of first 25 terms of an AP whose nth term is given by an=

1.	Find the sum of first 25 terms of an AP whose nth term is given by an= 7-3n
Answer» an=7-3na25=7-325a25=7-75a25=-68. (last term)a=7-31a=7-3a=4. (first term) Sn=n/2(a+l)S25=25/2[4+(-68)]S25=25/2[4-68]S25=25/2[-64]S25=25*-32S25=-800.Ans

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