Question

diketahui barisan 12,7,2 jumlah 15 suku pertama​

Answer 1

Verified answer

Jawab:

Penjelasan dengan langkah-langkah:

12, 7, 2, ...

a = 12

b = 7 - 12 = -5

Sn = (n/2) (2a + (n - 1)b)

S15 = (15/2) (2 (12) + (15 - 1) (-5))

S15 = (15/2) (24 - 14 (5))

S15 = (15/2) (24 - 70)

S15 = (15/2) (-46)

S15 = -345

Jadi, jumlah 15 suku pertama adalah -345.