1.diketahui suatu barisan geometri dengan u4=81 dan u6=729 tentukan rasionya,suku pertama,besarnya suku ke-10 2.Di tentukan besar suku pertama barisan geometri

1.
r^6-4 = 729/81 = 9
r² = 3²
r = 3
u4 = ar³ = 81
a = 81/(3³) = 3
U10 = 3 x 3^9 = 59.049

2.
r^5-1 = ⅔ ÷ 54 = ⅔ x 1/54 = 1/81
r⁴ = ⅓⁴
r = ⅓
a = 54

S8 = 54 x ( 1 - ⅓^8)/(1-⅓)
= 54/⅔ x ( 6.561/6.561 - 1/6.561)
= 54 x 3/2 x 6.560/6.561
= 81/6.561 x 6.560
= 6.560/81
= 80,987