Matematika

Pertanyaan

barisan aritmetika u6=18 u10=30 jumlah suku ke 16

2 Jawaban

  • U6 = 18
    U10 = 30

    Un = a + (n-1) b

    a + 5b = 18
    a + 9b = 30
    --------------- -
         -4b = -12
            b = 3

    a + 5b = 18
    a + 15 = 18
    a = 3

    U16 = 3 + 15 x 3
            = 3 + 45
            = 48
  • U10 = a + 9b
    30 = a + 9b

    U6 = a + 5b
    18 = a + 5b

    30 = a + 9b
    18 = a + 5b
    _________-
    12 = 4b
    b = 12/4
    b = 3

    a + 5b = 18
    a + 5(3) = 18
    a + 15 = 18
    a = 18 - 15
    a = 3

    U16 = 3 + 15 . 3
    U16 = 3 + 45
    U16 = 48

    Sn = n/2 ( 2.a + (n-1) . b)
    S16 = 16/2 (2.3+(16-1).3)
    S16 = 8 ( 6 + 45)
    S16 = 8 (51)
    S16 = 408

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