(tolong sertakan cara penyelesaiannya)
Tentukan besar suku kedelapan (U8) dan jumlah 8 suku pertama dari deret geometri berikut (S8) -18 + 6 – 2 + 2/3 + . . .
Jawaban Terkonfirmasi
a = – 18
r = 6/- 18 = – 1/3
U8 = a . r^(8 – 1)
= – 18 .(- 1/3)^7
= – 18 . - 1/ 2187
= 18/2187
= 2/243
S8 = – 18 [ 1 – (1/3)^8 ] / [1 – (- 1/3)]
= – 18 [ 1 – (1/6561) ] / (1 + 1/3)
= – 18 (6560 / 6561) / (4/3)
= – 18 (6560 / 6561) x 3/4
= – (27/2) x (6560 / 6561)
= – 3280 / 243