jumlah suatu deret geometri tak hingga adalah 10,jika u1=4,r=

==Jawaban==
Dik:
a = 4
S∞ = 10

Dit:
r = ?????????

Jwb:
S∞ = a/(1 - r)
10 = 4/(1 - r)
10(1 - r) = 4
10 - 10r = 4
10 - 4 = 10r
6 = 10r
r = 6/10
r = 3/5