mohon bang sekarang di kumpul tanggal 4-10-2017

a=1
r=1/2:1=1/2
Sn=a(1-r^n) /1-r
S7=1((1-(1/2)^7)) /1-1/2
=(1-1/128) x 2
=127/128 x 2
=254/128
=127/64
=1 63/64