Question

Tuliskan rumus suku "n" pada setiap barisan
1. 4,9,14,19 rumus=?
2.9,16,25,36 rumus=?

Answer 1

1) 4, 9, 14, 19 =
a = 4
b = 9 - 4 = 5
Un = a + (n - 1) b
= 4 + (n - 1) 5
= 4 + 5n - 5
= 5n + 4 - 5
= 5n -1

2) 9, 16, 25, 36 =
a = 9
r = 16/9
Un = ar^n-1
= 9.(16/9)^n-1
= 9. (16/9)^n - (16/9)
= (16/9)^n + 9/1 - (16/9)
= (16/9)^n - 7/9