Question

Diketahui barisan aritmatika 65, 58, 51, 44, … , –75. Banyaknya suku pada barisan tersebut adalah ...

Answer 1

A = 65
b = 58 - 65
= -7
Un = a + (n - 1) b = -75
= 65 + (n - 1) -7 = -75
= 65 -7n + 7 = -75
= 72 - 7n = -75
= -7n = -75 - 72
= -7n = -147
= n = -147/-7
Un = 21