A.Pada deret geometri , U1 = 18 , U3 = 2 . Tentukan U5 !! B.Diketahui Baris geometri , U4 = 40 , U6 = 160 . Tentukan U8!!

#A
Dik. U1 = 18 & U3 = 2
Dit. U5?

Jawab...

rasio (r) :
U1 = a = 18
U3 = a × r^2 = 2
----------------- :
@ r^2 = 1/9
@ r = 1/3

U5 = a × r^4
U5 = 18 × (1/3)^4
U5 = 18 × 1/81
U5 = 0,222

#B
Dik. U4 = 40 & U6 = 160
Dit. U8 ?

Jawab...

rasio (r) :

U6 = a × r^5 = 160
U4 = a × r^3 = 40
------------------------ :
@ r^2 = 4
@ r = 2

a (U1) :

a × r^3 = 40
a × (2)^3 = 40
a × 8 = 40
a = 40/8
a = 5

U8 = a × r^7
U8 = 5 × (2)^7
U8 = 5 × 128
U8 = 640

Semoga mebantu.. ^_^