If the sum of the first n terms of an AP is given by Sn=(3n²-n), find its nth term.​

If the sum of the first n terms of an AP is given by Sn=(3n²-n), find its nth term.​

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2 thoughts on “If the sum of the first n terms of an AP is given by Sn=(3n²-n), find its nth term.​”

  1. Given Sum of n terms is S

    n

    =3n

    2

    −4n

    So Sum of n−1 terms is S

    n−1

    =3(n−1)

    2

    −4(n−1)

    =3n

    2

    −6n+3−4n+4

    =3n

    2

    −10n+7

    Sum of n terms is equal to sum of n−1 terms plus n

    th

    term

    ⟹n

    th

    term =S

    n

    −S

    n−1

    =3n

    2

    −4n−(3n

    2

    −10n+7)

    n

    th

    term=6n−7

    Reply

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