Tentukanlah U125 Pada Barisan berikut a.100,105,110 b.25,15,5

Bab Barisan dan Deret
Matematika SMP Kelas IX

a] 100, 105, 100
b = 105 - 100
b = 5

Un = a + (n - 1) b
U125 = 100 + (125 - 1) x 5
U125 = 100 + 620
U125 = 720

b] 25, 15, 5, ...
b = 15 - 25
b = -10

Un = a + (n - 1) b
U125 = 25 + (125 - 1) x (-10)
U125 = 25 - 1.240
U125 = -1.215