Question

Tentukan banyak suku dari barisan berikut!
a. 6 + 9 +12 + 15 + … = 756
b. 56 + 51 + 46 + 41 + … = -36
c. 10 + 14 + 18 + 22 + … = 640

Answer 1

Sn= n/2(a+Un)
756 = n/2(6+(n-1)b)
756 = n/2(6+(n-1)3)
756 = n/2(6+3n-3)
756 = 3n+3n^2/2-3n/2
756 x2 = (3n+3n^2/2-3n/2)2
3n^2-3n-1512=0