Diketahui barisan geometri u3=3 & u5=27.hitunglah jumlah 5 suku pertamanya?

Un = ar^n-1

U5/U3 = 27/3
ar^4/ar^2 = 9
r^2 = 3

U3 = 3
ar^2 = 3
a(3)^2 = 3
9a = 3
a = 1/3

Sn = a(r^n -1)/r-1
S5 = 1/3 ( (3)^5 -1)/3-1
S5 = 1/3 (243-1)2
S5 = 1/3 (242) / 2
S5 = 1/3 x 121
S5 = 40 1/3

inshaallah:), maf kalau salah

U₃ = a . r² = 3
U₅ = a . r⁴ = 27
lakukan pembagian :
r² = 9
r = 3

a . r² = 3
a . 9 = 3
a = 3 / 9
a = 1/3

Sn = a (rⁿ - 1) / r - 1
S₅ = a (r⁵ - 1) / r - 1
S₅ = 1/3 (3⁵ - 1) / 3 - 1
S₅ = 1/3 (243 - 1) / 2
S₅ = (243 - 1) / 2 . 3
S₅ = 242 / 6