an ap has 5,12,19-.has 50 terms find its last term ​

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an ap has 5,12,19…..has 50 terms find its last term

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Ivy 1 month 2021-08-19T02:10:12+00:00 1 Answer 0 views 0

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    2021-08-19T02:12:02+00:00

    Answer:

    a = 5

    d = 12 – 5 = 7

    n = 50

    an = a + (n – 1)d

    an = 5 + (50 – 1)7

    an = 5 + 49*7

    an = 5 + 343

    an = 348

    Sum of the last 25 terms –

    a = 348, d = – 7, n = 15

    Sn = n/2[2a + (n – 1)d]

    Sn = 15/2[2*348 + (15- 1) – 7]

    Sn = 7.5[696 + (14 × – 7)]

    Sn = 7.5[696 – 98]

    Sn = 7.5*598

    Sn = 4485

    Sum of the last 15 term is 4485

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