Question

Diketahui siatu barisan bilangan 5,2,-1,......,-52
tentukanlah jumlah dari barisan tersebut

Answer 1

Verified answer

Kelas 8 Matematika
Bab Barisan dan Deret Bilangan

b = U2 - U1
b = 2 - 5
b = -3

Un = -52
a + (n - 1) . b = -52
5 + (n - 1) . (-3) = -52
(n - 1) . (-3) = -52 - 5
n - 1 = -57/-3
n = 19 + 1
n = 20

Sn = n/2 . (a + Un)
S20 = 20/2 . (5 + (-52))
S20 = 10 . (-47)
S20 = -470