tolong bantuin aku dong pake caranya

Jadi, jawabannya adalah c

jawab

Sn = 2. 3²ⁿ - 2
Sn = 2 (3²ⁿ -1)

a= s1 = 2(3² -1) = 2(8) = 16
s2 = 2(3⁴ -1) = 2(80) = 160

a + ar = 160
a(1 + r) =160
16( 1+ r)  = 160
1+ r = 10
r = 9