dik:u4=10/9 u6=10/81 DIt:u1 dan rasio dan barisan u10??

U4=ar^3=10/9
U6=ar^5=10/81

ar^5=ar^3•r^2=10/81
=10/9•r^2=10/81
= r^2=10/81•9/10
= r^2=1/9
= r=1/3 (rasio)

ar^3=10/9
a(1/3)^3=10/9
a•1/27=10/9
a=10/9•27
a=30 (U1)

U10=ar^9= 30•(1/3)^9= 30•1/19683=152/100000=76/50000=38/25000=19/12500

U4 = a x r x r x r

U6 = a x r x r x r x r x r
U6 = U4 x r x r
10/81 = 10/9 x r^2
r^2 = 10/81 x 9/10
r^2 = 9/81
r = 3/9 atau 1/3

lalu cari a atau U1,
U4 = a x r x r x r
10/9 = a x 1/3 x 1/3 x 1/3
10/9 = a x 1/27
a = 10/9 x 27/1
a = 30

U10 = a x r^9
U10 = 30 x (1/3)^9
U10 = 30 x 1/19683
U10 = 10/6561