Hitunglah Sn dari deret-deret geometri berikut ini: A. 1 + 4 + 16 + ... (n = 8) B. 5 + 10 + 20 + ... (n = 6 ) C. 300 + (-150) + 75 + ... (n = 7) D. 1/1

A)
a = 1
r = 4/1 = 4
S8 = 1 x (4^8 - 1)/(4-1)
= (65.536-1)/3
= 65.535/3
= 21.845

B)
a = 5
r = 10/5 = 2
S6 = 5 x (2^6 -1)/(2-1)
= 5 x (64-1)/1
= 5 x 63
= 315

C)
a = 300
r = -150/300 = -½
S7 = 300 x ( 1 - ½^7)/(1-½)
= 300 x (1 - 1/128)/½
= 300x2x(128-1)/128
= 600 x 127/128
= 595,3125

D)
a = 1/16
r = ¼/(1/16) = ¼ x 16/1 = 16/4 = 4
S10 = 1/16 x ( 4^10 - 1)/(4-1)
= 1/16 x (1.048.576 -1)/3
= 1/16 x 1.048.575/3
= 349.525/16
= 21.845,3125