Deret Geometri gan.. penjelasannya yak..!

Diketahui:

⇒
U1 = a
54 = a
a = 54 ... (i)

⇒
U3 = ar²
6 = ar²
ar² = 6

⇒ Eliminasi:
ar² = 6
a = 54  :
r² = 1/9
r = √(1/9)
r = 1/3, r < 1

⇒ Jumlah 5 suku pertama:
Sn = [a (1 - r^n)] / (1 - r)
S5 = [54 (1 - (1/3)^5)] / (1 - 1/3)
S5 = [54 (1 - 1/243)] / (2/3)
S5 = [54 (242/243)] / (2/3)
S5 = (13068/243) / (2/3)
S5 = 13068/243 * 3/2
S5 = 39204/486
S5 = 80 (2/3)

Jadikan Yang Terbaik Aaaaaa :D