Suatu barisan geometri di ketahui suku ke empat 10/9 dan suku ke enam 10/81 tentukan besar suku ke 8

U4 = ar³ = 10/9

U6 = ar^5
10/81 = ar³.r²
10/81 = 10/9 . r²
r² = 10/81 ÷ 10/9
r² = 10/81 × 9/10
r² = 1/9
r = √ 1/9
r = ⅓

U4 = ar³
10/9 = a. (1/3)³
10/9 = a . 1/27
a = 10/9 ÷ 1/27
a = 10/9 × 27/1
a = 30

U8 = ar^7
= 30 . (1/3)^7
= 30 . 1/2187
= 30/2187