Jawabanmu

2014-05-30T11:52:40+07:00
a.r^12/a.r^6=512/64 lalu cari rasionya
terus ar^6=64 jadi a.8=64 jadi a= 8 ....

maaf kalau salah
1 5 1
2014-05-30T13:19:52+07:00
U13/U7 = 512/64
r^6 = 8
r = √2
a = 8
S5 = 8 + 8√2 + 16 + 16√2 + 32 = 56 + 24√2