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The 4th term of an arithmetic sequence is 1. The 10th term of the same sequence is -2. Which is an explicit formula for this sequence?

 Feb 22, 2020
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1 = F + D*(4 - 1),   
-2=F + D*(10 - 1), solve for F, D


F =5/2 - First term.
D = - 1/2 - Common difference.


a(n) =[6 - n] / 2 ...... and your sequence contiues....

5/2, 2, 3/2, 1, 1/2, 0, -1/2, -1, -3/2, -2, -5/2, -3, -7/2, -4, -9/2, -5, -11/2, -6, -13/2, -7, ...
     

 Feb 22, 2020

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