U3=10 U6=5/4 Tentukan U8? pliss kak bantu

U3 = 10
10 = a * r²
a = 10 / r²

U6 = 5/4
5/4 = a * r^5
5/4 = 10 / r² * r^5
5/4 * 1/10 = r^5 / r²
1/8 = r³
r = 1/2
a = 10 / 1/4 = 40

U8 = a * r^7
U8 = 40 * (1/2)^7 = 40 * 1/128 = 5/16

maaf kalau salah