Jawabanmu

2014-02-27T14:58:49+07:00
Suku berurutan 1/4dan 1/2, maka rasionya 1/2:1/4 = 2

jika r =2 maka
U8 = 2
ar⁷ = 2
a.2⁷= 2
a = 2/2⁷
a = 1/2⁶
a= 1/64

maka, 
Sn = a(r⁸ - 1) / r - 1
S₈ = 1/64(2⁸-1) / (2 - 1)
S₈ = 1/64 (256 - 1) / 1
S⁸ = 255/ 64

semoga membantu

1 5 1
2014-02-27T15:50:01+07:00
 S_{8} =n/2(a+ U_{8} )
 S_{8} =8/2(1/4+2)
                        =4(9/4)
                         =9


1 5 1