Jumlah 13 suku pertama barisan bilangan : 6, 11, 16, 21, …. adalah​

Jawaban:

6 , 11 , 16 , 21 , …

a = 6

b = 11 – 6 = 5

Sn = n/2 . [2a + (n – 1) b]

S13 = 13/2 . [2(6) + (13 – 1) 5]

S13 = 13/2 . (12 + 60)

S13 = 13/2 . (72)

S13 = 468