tolong bantu jawab ya

6)
U1 = 2^(1-1) = 2^0 = 1
U2 = 2^(n - 1) = 2^1 = 2
r = U2/U1 = 2/1 = 2
Sn = a(r^n - 1) / r-1
S7 = 1(2^7 - 1) / 2-1
= 128 - 1
= 127

7) Sn = 3^n - 1
U1 = S1 = 3^1 - 1 = 3 - 1 = 2
S2 = 3^2 - 1 = 9 - 1 = 8
U2 = S2 - S1 = 8 - 2 = 6
r = U2/U1 = 6/2 = 3
Un = ar^(n-1)
U5 = 2.(3)^4
U5 = 2.81 = 162
atau bisa cara lain
U5 = S5 - S4
U5 = 3^5 - 1 - (3^4 - 1)
= 243 - 1 - (81 - 1)
= 243 - 81
= 162