Matematika

Pertanyaan

dik deret aritmatika dan suku ke7=20 Dan suku ks5 + suku ke8=74. suku ke 50 barisan tsb adalah?

2 Jawaban

  • langsung aja ya

    U7 = 20 => a + 6b = 20

    U5 + U8 = 74
    => a + 4b + a + 7b = 74
    => 2a + 11b = 74


    a + 6b = 20 |×2|
    2a + 11b = 74 |×1|

    2a + 12b = 40
    2a + 11b = 74
    ____________ __
    b = -34

    suku ke 50

    U50 = U7 + (50-7)×b
    U50 = 20 + 43×(-34)
    U50 = 20 + (-1462)
    U50 = -1442
  • langsung aja ya

    U7 = 20 => a + 6b = 20

    U5 + U8 = 74
    => a + 4b + a + 7b = 74
    => 2a + 11b = 74


    a + 6b = 20 |×2|
    2a + 11b = 74 |×1|

    2a + 12b = 40
    2a + 11b = 74
    ____________ __
    b = -34

    suku ke 50

    U50 = U7 + (50-7)×b
    U50 = 20 + 43×(-34)
    U50 = 20 + (-1462)
    U50 = -1442

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