Question

for what value of n are the nth terms of the sequences5,10,20... and 1280,640,,320....equal

Answer 1

In the first sequence each number is multiplied by 2 and in the second sequence each number is divided by 2. So, in the first sequence we get 5, 10, 20, 40, 80, ... and in the second sequence we get 1280, 640, 320, 160, 80,... So in the both sequences the 5th term is equal. So, the value of n=5.

Answer 2

Answer:

solution

Step-by-step explanation:

G.P is given

a,ar,ar^2,------- ,ar^n-1

In the sequence 5,10,20,40,------

first term (a) =5

common ratio (r) = 10/5 = 2

equate the term to be found with the n,nth term

ar^n-1 = 1280

5×2^n-1= 1280

2^n-1 =256

n-1=8

n=9

9th term is equal