tolong di jawab ya teman teman

Kelas 8 Matematika
Bab Barisan dan Deret Bilangan

r = U2/U1
r = 14/28
r = 1/2

Sn = a . (1 - rⁿ)/(1 - r)
S8 = 28 . (1 - (1/2)⁸) / (2/2 - 1/2)
S8 = 28 . (256/256 - 1/256) / (1/2)
S8 = 28 . 255/256 . 2
S8 = 1.785/32
S8 = 55  25/32