hitungla deret geometri berikut 1-3+9-.....smapai 12 suku

Sn (ganjil) = a (r^n - 1) / (r-1)
= 1 (3^6 - 1) / (3-1) = 728/2 = 364

Sn (genap) = a (r^n - 1) / (r-1)
= -3 (3^6 -1) / (3-1) = -2184/2 = -1092

jadi hasilnya 364 + (-1092) = -728