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Find the number of terms in the sequence.

 

-18, 36,-72,...,9437184

 May 4, 2021
 #1
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-1

Let's focus on every other number. 
We have: 36, 90, 144, ... 9437184.

The common difference is 54, so let's set every to a multiple of 54.

54, 108, 162, ... 9437202.

Dividing these terms by 54, we get:

1,2,3,...174763.

Remember, we are counting every other number, so there are really:

174763 * 2 = 349526 terms in the sequence.

 May 4, 2021
 #2
avatar+26399 
+2

Find the number of terms in the sequence.
18, 36, 72,  , 9437184

 

My attempt:

sequence:9182=(2)1364=22728=(2)394371841048576=220

 

Formula:an=9(2)na20=9(2)20a20=9220a20=91048576a20=9437184

 

There are 20 terms in the sequence.

 

laugh

 May 4, 2021
edited by heureka  May 4, 2021

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