Untuk barisan geometri berikut tentukan duku ke n yg di tunjukan pada kolom ke 3 dengan menggunakan rumus! Barisan geometri. Suku ke N A.7,14,28,56

Penyelesaian:

dapat di cari menggunakan rumus Un geometri:
Un = a.r^n-1

a. barisan bilangan: 7, 14, 28, 56, ...
a = 7 ; r = 2
U9 = 7.2^9-1
= 7.2^8
= 7.256
U9 = 1,792

b. barisan bilangan: 2, 8, 32, 128, ...
a = 2 ; r = 4
U7 = 2.4^7-1
= 2.4^6
= 2.4096
U7 = 8,192

c. barisan bilangan: 108, 36, 12, 4, ...
a = 108 ; r = 1/3
U8 = 108.(1/3)^8-1
= 108 . (1/3)^7
= 108 . (1/2187)
U8 = 108/2187

d. barisan bilangan: 8, 12, 18, 27, ...
a = 8 ; r = 3/2
U8 = 8.(3/2)^8-1
= 8.(3/2)^7
= 8.(2187/128)
U8 = 2187/16

e. barisan bilangan: -2, -6, -18, -54, ...
a = -2 ; r = 3
U9 = (-2).(3)^9-1
= (-2).(3)^8
= (-2).(6561)
U9 = -13,122

f. barisan bilangan: 4, -12, 36, -108, ...
a = 4 ; r = -3
U9 = 4.(-3)^9-1
= 4.(3)^8
= 4.(6561)
U9 = 26,244

A.U9 :
= a x r^ⁿ-¹
= 7 x 2^9-1
= 7 x 2^8
= 1.792

B.a=2
r=4
U7= 2(4)^6=8192

C.U8=arpangkat 7
U8=108.3pangkat7
U8=108.2187
U8=236196

D.(8×3)÷ 2 = 12
(12×3)÷ 2 = 18
(18×3)÷ 2 = 27
(27×3)÷ 2 = 40.5

F.a= 4
r= 3
un=a.rn-1
u8=4.3 pangkat 8-1
u8= 4. 3 pangkat 7
u8= 4. 2187
u8=8748

E.Un = 4 × 3^n-1

Maka,
4 × 3^n-1 = 2.916
3^n-1 = 2916/4
3^n-1 = 729
n-1 = 6
n = 6 + 1
n = 7

#smogamembantu
#smangatt