R = U2/U1
= 6/3
= 2

Un = a.r^n^-^1
384 = 3.2^n^-^1
384:3 = 2^n^-^1
128 = 2^n^-^1
2^7 = 2^n^-^1
7 = n-1 (Ket: angka 2 itu sama-sama dicoret)
7+1 = n
8 = n

S8 = a(r^n-1)/(r-1)
= 3(2^8-1)/(2-1)
= 3(256-1)/(1)
= 3*255*1
= 765*1
= 765

Jawabanmu

2014-03-01T08:53:36+07:00
Maaf kalau salah.
3+6+12.............+384
3+6+12+24+48+96+192+384  = 765
2014-03-01T11:33:14+07:00
3+6+12.............+384
3+6+12+24+48+96+192+384  = 765