Soal Matematika Kelas 11 Halaman 202, 203 Uji Kompetensi 5.2 Barisan dan Deret Geometri

= 54(1 – (1/3)^9) / (1 – 1/3)

= 54 ( 1 – 1/19.683) / 2/3

= 81 ( 19.682/19.683)

= 19.682 / 243

= 80,996

c. a1 = 5 dan r1 = 9

a2 = -15 dan r2 = 9

S4 pertama = 5 (9^4 – 1) / (9-1) = 5 (6561 – 1) / 8 = 4100

S4 kedua = -15 (9^4 – 1) / (9-1) = -15(6561 – 1) / 8 = -12.300

S gabungan = 4.100 – 12.300 = – 8.200