Diketahui barisan 3,4,7,12,19,... nilai suku ke-12 berdasarkan pola barisan tersebut adalah... A. 124 B. 122 C. 114 D. 103 tolong dijawab terima kasih :)

Kelas 8 Matematika
Bab Barisan dan Deret Bilangan

3, 4, 7, 12, 19, ... → a = 3
...1,..3,..5,..7,... → b = 1
.....2...2...2... → c = 2

n = 12

Un = a + (n - 1) . b + 1/2 . (n - 1) (n - 2) . c

U12 = 3 + 11 . 1 + 1/2 . 11 . 10 . 2
U12 = 3 + 11 + 110
U12 = 124

✩✩ A ✩✩