Diketaui deret arimatika 27+24+21+ jumblah 20 suku pertama (S20) adlh

Mapel : Matematika
Bab : Barisan dan Deret

Deret Aritmatika

a = 27
b = 24 - 27 = -3

  Sn = n/2 ( 2a + (n-1) b )
S20 = 20/2 ( 2.27 + (20-1) -3)
S20 = 10 ( 54 + (-57) )
S20 = 20 x (-3)
S20 = -60