tolong bantuin no 2 plissss....

a = 22
b = 8
S20 = 20/2 [ 2×22 + (20-1)8]
= 10[44+152] = 10(196)=1960

Dik : a = 22 kursi, b = 8 kursi
Dit : S20?
Jawab : Sn = n/2 (2a+(n-1)b)
            S20= 22/2 (2.22 + (22-1)8)
            S20= 11 (42 + 168)
            S20= 11 (210) = 2310 kursi.

ini jawaban saya