barisan arimatika 0,3,6,9 a)suku ke 11 b) jmlh suku ke 8 tolong y

A = 0
B = 3-0 = 3

U11 :
= a + 10b
= 0 + 10x3
= 0 + 30
= 30

S8 :
= n/2 [a x b + (n-1) x b]
= 8/2 [0 x 3 + (8-1) x 3]
= 4 [0 + 7 x 3]
= 4 x 21
= 84