Question

1. tentukan rumus suku ke n dari barisan-barisan berikut :
a. 3/5,6/15,12/45,24/135

2. tentukan lima suku pertama dari suatu barisan yg rumus suku ke n adl Un= 2×3(n-1)

Answer 1

A. a = 3/5
   r = U2/U1 = 6/15 : 3/5 = 6/15 x 5/3 = 2/3
Un = ar^(n-1) = 3/5 x (2/3)^(n-1)
b. U1 = 2 x 3 (1 - 1) = 2 x 0 = 0
   U2 = 2 x 3 (2 - 1) = 6
   U3 = 2 x 3(3-1) = 12
   U4 = 2 x 3 (4-1) = 18
   U5 = 2 x 3 (5 - 1) = 24

Answer 2

R= 6/15/3/5 = 6/15 x 5/3 = 2/3
Un = ar^n-1
= 3/5 x 2/3^n-1

2. Un = 2x3(n-1)
U5 = 2x3(5-1)
U5 = 2x3x4 = 24