Question

Diketahui deret geometri 20, 10 ,5 ,5/2, tentukan rasio suku ke 8 dan jumlah 8 suku pertama...

Answer 1

Verified answer

Kelas 8 Matematika
Bab Barisan dan Deret Bilangan

1] r = U2/U1
r = 10/10
r = 1/2

2] U8 = a . r⁷
U8 = 20 . (1/2)⁷
U8 = 20 . 1/128
U8 = 5/32

3] Sn = a . (1 - rⁿ) / (1 - r)
S8 = 20 . (1 - (1/2)⁸) / (2/2 - 1/2)
S8 = 20 . (256/256 - 1/256) / (1/2)
S8 = 20 . 255/256 . 2
S8 = 1.275/32
S8 = 39  27/32