Matematika

Pertanyaan

5. Carilah enam suku pertama dari barisan geometri berikut
a. a = 2; r =1/2
b. a = 12; r =1/3

1 Jawaban

  • 5a) Un = ar^n-1
    U1 = a = 2
    U2 = ar = 2 • ½ = 1
    U3 = ar² = 2 • ( ½ )² = 2 • ¼ = ½
    U4 = ar³ = 2 • ( ½ )³ = 2 • 1/8 = ¼
    U5 = ar⁴ = 2 • ( ½ )⁴ = 2 • 1/16 = 1/8
    U6 = ar^5 = 2 • ( ½ )^5 = 2 • 1/32 = 1/16
    barisanya 2 , 1 , ½ , ¼ , 1/8 , 1/16

    b) U1 = a = 12
    U2 = ar = 12 • ⅓ = 4
    U3 = ar² = 12 • ( ⅓ )² = 12 • 1/9 = 12/9 = 4/3
    U4 = ar³ = 12 • ( ⅓ )³ = 12 • 1/27 = 12/27 = 4/9
    U5 = ar⁴ = 12 • ( ⅓ )⁴ = 12 • 1/81 = 12/81 = 4/27
    U6 = ar^5 = 12 • ( ⅓ )^5 = 12 • 1/243 = 12/243 = 4/81
    barisanya = 12 , 4 , 4/3 , 4/9 , 4/27 , 4/81

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