Tolong yaa kaa no 1, 2 dan 3. Geometri

Soal No. 1 Barisan geometri: -1, 3, -9, 27, ... a = -1 r = 3/-1 = -3 Un = a. r^(n-1) U10 = a. r⁹ U10 = (-1) (-3)⁹ U10 = 19683 Sn = a(r^n -1)/ r-1 S1 = a = -1 Soal No. 2 U9 = 128 --> ar⁸ = 128 ——————————— : U4 = 4 --> ar³ = 4 r⁵ = 32 r = ⁵√32 = 2 U4 = 4 ar³ = 4 a. 2³ = 4 a = 4/8 = 1/2 U7 = ar⁶ U7 = 1/2 × (2⁶) U7 = 1/2 × 64 U7 = 32 S5 = a (r⁴ - 1)/( r - 1) S5 = ½ ( 2⁴ -1 )/ ( 2 -1) S5 = ½ (16 -1 ) / 1 S5 = 15/2 = 7,5 Soal No. 3 Awal ada 10 virus --> a = 10 Membelah menjadi 2 --> r = 2 Membelah tiap 12 jam Kalau ada 4 hari = 4 × 24 jam = 96 jam Berapa kali membelah = 96 jam : 12 jam = 8 kali Maka n = 1 + 8 = 9 Jumlah virus setelah 4 hari = U9 = ? U9 = ar⁸ U9 = 10 (2⁸) U9 = 10 × 256 U9 = 2560 virus Hasil akhir ada 2560 virus setelah 4 hari