Question

No 2 gmn ya?(pake cara)

Answer 1

Verified answer

Mapel Matematika
Bab Baris dan Deret

Sn = 1218
a = 8
b = 5

Sn = n/2 (2a + (n - 1)b)
1218 = n/2 (16 + 5n - 5)
2436 = n(11 + 5n)
2436 = 11n + 5n^2
5n^2 + 11n - 2436 = 0
(5n + 116)(n - 21) = 0

n = -116/5 atau n = 21

Ambil yg positif, jadi n adalah 21