17.Ifthe sum offirst n terms ofan A.P is given by Sn-3n2+5n, find the – InterviewSolution

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17.Ifthe sum offirst n terms ofan A.P is given by Sn-3n2+5n, find the nth term ofthe A.P

Answer»

The sum of n terms of an A.P. = 3n²+5n

then sum of n-1 terms= 3(n-1)²+5(n-1)

So nth term of A.P will be

T(n) = 3n² + 5n - 3(n-1)²-5(n-1)

= 3n²+5n-3n²-3+6n-5n+5

=6n+2

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