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jawab
deret geo
24.
 s~= 27
a = 18

s~ = a/ ( 1 - r)
1 - r = a/s~
1- r  = 18/27 = 2/3
r = 1 - 2/3
r = 1/3


25. 
deret geometri
u2 = 12
u3 = 9

u3 / u2 = 9/12
r = 9/12 = 3/4

u2 = 12
r = 3/4
a = u2/r
a= 12/(3/4)
a= 4/3. 12
a = 16

S~ = a/ (1 - r)
s~ = 16 / (1 - 3/4)
s~ = 16/(1/4)
s~ = 4(16) = 64