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Bab Barisan dan Deret
Matematika SMP Kelas IX

Geometri
r = 112/14 = 8

Sn = a x (r^n - 1) / (r - 1)
Sn = 14 x (8^n - 1) / (8 - 1)
Sn = 2 x 2^(3n) - 2
Sn = 2^(3n + 1) - 2

jawabannya A