Question

QUIZ #97
Materi: Barisan dan Deret

Diketahui suatu barisan aritmatika -2, 1, 4, ... dan seterusnya. Tentukan jumlah 20 suku pertama barisan tersebut!​​

Answer 1

Verified answer

a = -2

b = 1 - (-2) = 1 + 2 = 3, 4 - 1 = 3

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

S20 = 20/2(2(-2) + (20 - 1)3)

S20 = 10(-4 + 57)

S20 = 10(53)

S20 = 530.