Hitunglah jumlah deret aritmatika berikut -16 + -12 + -8 + -4 jika banyak sukunya 20

Kelas 8 Matematika
Bab Barisan dan Deret Bilangan

b = U2 - U1
b = -12 - (-16)
b = 4

Sn = n/2 . (2a + (n - 1) . b)
S20 = 20/2 . (2 . (-16) + 19 . 4)
S20 = 10 . (-32 + 76)
S20 = 10 . 44
S20 = 440

b=-12+16=4

Sn=1/2 n (2a + (n-1) . b)
S20= 1/2. 20 (-32 + (19).4)
      = 10 x 44
      = 440