Answers

2014-04-26T23:07:22+05:30
Tn=3n+5 = 8+3n-3 = 8+(n-1)*3. therefore a=8 and d=3.
Hence Sn=n/2(2a+(n-1)d) = n/2(16+3n-3) = n/2(13+3n) = (13n+3n^2)/2. 
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