tentukan jumlah deret 5+8+11+......+ 47

Dik. barisan deret aritmatika : 5+8+11+.... + 47
Dit. Sn ?

Jawab...

Beda (b) = U2-U1 = 8-5 = 3

Sn = n/2 (2a + (n-1) (b)
S47 = 47/2 (2(5) (47-1) (3))
S47 = 47/2 (10 + (46) (3))
S47 = 47/2 ( 10 + 138)
S47 = 47/2 (148)
S47 = 3478

Semoga membantu... ^_^