Tolong dijawab yhh Semuanya

Penyelesaian:

Sn = 2^n + 1

U1 = S1

S1 = 2^1 + 1 = 3  (suku awal)  B.
S2 = 2^2 + 1 = 5

S2 - S1 = U2
5 - 3 = 2 (suku kedua)  B.

Un = a.r^n-1
2 = 3.r^2-1
2 = 3r
r = 2/3  (rasio)  C.

Un = a.r^n-1
= 3 . (2/3)^n-1
= 3 . (2/3)^n . 3/2
Un = 9/2 (2/3)^n  (rumus Un) A.