Tentukan banyaknya suku dr barisan geometri 1/4,1/6,9....4/81.... Question from @linne

September 2018 2 21 Report

Tentukan banyaknya suku dr barisan geometri 1/4,1/6,9....4/81

Ikaikariskha Rasio: u2:u1 = 1/6:1/4 = 2/3
Un= ar^n-1
4/81=1/4((2/3)^n-1
4/81:1/4=(2/3)n-1
16/81= (2/3)^n-1
(2/3)^4=(2/3)^n-1
2/3 nyadi coret kanan kiri
Jadi, 4=n-1 --->> n=5

1 votes Thanks 1

Mausuf Apa maksud barisan sebenarnya itu begini ?
$\frac{1}{4} , \frac{1}{6} , \frac{1}{9} ,..., \frac{4}{81}$
Rasio : $r= \frac{U_2}{U_1} = \frac{ \frac{1}{6} }{ \frac{1}{4} }= \frac{1}{6}* \frac{4}{1}= \frac{4}{6}= \frac{2}{3}$
$a= \frac{1}{4}$
$U_n= \frac{4}{81}$
$\frac{1}{4}(\frac{2}{3})^{n-1}=\frac{4}{81}$
$(\frac{2}{3})^{n-1}=\frac{4}{81}*4$
$(\frac{2}{3})^{n-1}=\frac{16}{81}$
$(\frac{2}{3})^{n-1}=(\frac{2}{3})^4$
$n-1=4$
$n=4+1$
$n=5$

2 votes Thanks 1

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