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Let a1, a2, a3, ..., a10 be an arithmetic series.  If a1 + a3 = -2 and a2 + a4 + a6 = 1, then find a1.

 May 13, 2024
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avatar+9674 
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Suppose d=a2a1. Note that the given conditions are equivalent to:

{a1+d=1a1+3d=13

 

Solving gives d=23 and a1=53.

 May 13, 2024

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