Jawabanmu

2014-03-25T10:22:05+07:00
2014-03-25T10:38:21+07:00
Jumlah n suku petama deret geometri:

Sn = a  \frac{ (1-r^{n}) }{1-r}
a = suku pertama = -16
r = rasio =  \frac{1}{2}  

S20 = -16  \frac{(1-  \frac{1}{2} ^{20} )}{1- \frac{1}{2} } =


-16  \frac{(1-  (2^{-20}) )}{ \frac{1}{2} } = -  2^{5}(1- (2^{-20}) ) =   -  2^{5} +  2^{-15} = -32 +  \frac{1}{ 2^{15}}