Question

Tentukan banyak suku dan jumlah barisan aritmatika berikut!
a.-12-8-4-0+...+108
b.-3-7-11-15...-107

Answer 1

A.
a = -12
b = -8 -(-12) = 4
Un = 108
a + (n-1)b = 108
-12 + (n-1) 4 = 108
(n-1) 4 = 120
n - 1 = 30
n = 31
b.
a = -3
b = -7 - (-3) = -4
Un = -107
a + (n-1)b = -107
-3 + (n-1) -4 = -107
-4(n-1) = -104
n-1 = 26
n = 27