carilah jumlah 6 suku pertama pada riao deret geometri berikut ini. a. 8+4+2+... b. 2+3+9/2+...

a. a = 8
r = 1/2
n= 6
[tex]s6 = \frac{n}{2} .(2a + (n - 1).b) \\ = \frac{6}{2} (2(8) + (6 - 1) \frac{1}{2} ) \\ = 3(16 + \frac{5}{2}) \\ = 3( \frac{37}{2} ) \\ \frac{111}{2} = 55.5[/tex]
b. a = 2
r = 3/2
n= 6
[tex]s6 = 3(2(2) + 5( \frac{3}{2} )) \\ = 3(4 + \frac{15}{2} ) \\ = 3( \frac{23}{2} ) \\ = \frac{69}{2} = 34.5[/tex]