suku ke 24 dari 3,10,19,30

Kelas 8 Matematika
Bab Barisan dan Deret Bilangan

3, 10, 19, 30, ... → a = 3
...7....9....11... → b = 7
......2...2... → c = 2
n = 24

Un = a + (n - 1) . b + 1/2 . (n - 1) (n - 2) . c
U24 = 3 + 23 . 7 + 1/2 . 23 . 22 . 2
U24 = 3 + 161 + 506
U24 = 670