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posted by Embraced on Wednesday, January 11, 2012 at 7:18pm.
Find a1 for the arithmetic series with Sn = 77, an=30, and n-7
Just as in your other post, Sn = n/2 (a1 + an) Only this time we want a1 77 = 7/2 (a1 + 30) 154 = 7a1 + 210 -56 = 7a1 a1 = -8
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