Question

Deret geometri : 10+5+2 2/1+1 1/4+5/8+.....
jumlah 7 suku pertama deret tersebut adalah...

Answer 1

R= U2/U1 Sn= a*(1-r^n)/(1-r) S7=10*(1-0,5^7)/(1-0.5)=19,843

Answer 2

A = 10
r = 1/2
S7 = a (1+r^n) / 1 + r
     = 10 (1+1/2^7) / 1 + 1/2
     = 10 (1+1/128) / 3/2
     = 10 (129/128) / 3/2
     1290 / 128 per 3/2
     = 430/64 = 215 /32