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January 30, 2015

January 30, 2015

Posted by **alicia** on Monday, May 31, 2010 at 7:42pm.

- math sequences and series -
**Damon**, Monday, May 31, 2010 at 9:20pma1 + a2 = 16

a2 + a3 = 28

and since it is an arithmetic sequence

a2 - a1 = a3 - a2

or

a2 = (a1+a3)/2 (the average of course)

substitute back

a1 + (a1+a3)/2 = 16

(a1+a3)/2 + a3 = 28

solve those two equations for a1 and a3, then go back and get a2

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