Diketahui barisan bilangan -8,-5,-2,1,…. Tentukan jumlah 30 suku pertama.

Diket
a = -8
b = U2 – U1
= -5 – (-8)
= -5 + 8
= 3

S30 = n/2 (2a + (n-1)b)
= 15 (2 × -8 + (29)3)
= 15 ( -16 + (87))
= 15 ( 71 )
= 1.065