find the rth term of an ap, sum of whose first term is 2n + 3n^2
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The sum of first terms is = first term
Therefore your answer is a+5d-d
Therefore your answer is a+5d-d
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Tn = Sn - Sn-1
Similarily
Tr = Sr - Sr-1
Hence
Tr = 2r + 3r^2 - (2(r-1) + 3(r-1)^2)
Tr = 2r + 3r^2 -2r +2 - 3r^2 -3 + 6r
Tr = -1 +6r