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In an arithmetic sequence, the first term is 100 and the fourth term is 76. What is the value of the first term that is less than 0?

 Jan 10, 2020
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We can find the common difference as

 

76  -100          -  24

_______  =       ___    =   -  8

     3                   3

 

 

So  we need to solve this

 

100 -  8(n - 1)  =  0

 

100 - 8n + 8  =0

 

108  - 8n  = 0

 

54 - 4n  =  0

 

54  = 4n

 

54/4   = n

 

27/2  = n

 

13.5  = n

 

The  14th term will be < 0   ......so

 

100 - 8 (14 - 1)  =

 

100 - 8 * 13  =

 

100 - 104   =

 

-4

 

 

cool cool cool

 Jan 10, 2020

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