Given the sequence {-1, 3, 7, 11, …}, find a25

Question

Given the sequence {-1, 3, 7, 11, …}, find a25

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Thu Thủy 3 years 2021-08-09T14:48:35+00:00 1 Answers 18 views 0

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  1. vankhanh
    0
    2021-08-09T14:50:10+00:00
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    here,

    a1=-1

    a2=-1+4 =3

    a3= 3+4=7

    a4=7+4=11

    using the general formula for nth term of an ap

    an = - 1 + (n - 1)d \\ here \: a = - 1 \: and \: d = 4 \\ \\ an = - 1(n - 1)(4) = - 1 + 4 - 4 \\ 4n - 5 \\ \\ hence \: a25 = \\ 4(25) - 5 = 100 - 5 = 95

    Answer= a25 = 95

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