Bantu jawab pertannyaan no 30 gan

Diketahui :
a= 3
b = 5
Jawab :
Un = a + (n-1)b
68 = 3 +(5n-5)
68-3+5 = 5n
70 = 5n
n= I4

Sn = n/2 (2a+(n-1)b)
S14= 14/2 (2(3)+13(5)
S14= 7(6+65)
S14=7(71)
S14=497

Jawaban B