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2. Find the sum of the first 14 terms of the series  11 + 7 + 3 +

 Apr 17, 2019
 #1
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The common difference is -4

 

The 14th term is

 

11 -4(14 - 1)  =

11 - 4(13)

11 - 52 

-41

 

So.....the sum of the first   14 terms  =

 

[ first term + last term] * number of terms  / 2    =

 

[ 11 - 41 ] * 14  / 2  =

 

[ -30 ] * 7  =

 

-210

 

 

cool cool cool

 Apr 17, 2019

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