the 8th term is 5 differences from the 3rd term, and 7 differences from the 1st term
e = 2 t = 2 (f + 2 d)
f + 7 d = 2 f + 4 d
... 3 d = f
sum8 = 8 f + 28 d = 39
substituting ... 24 d + 28 d = 39
... 52 d = 39 ... d = 3/4
substitute back to find f
The eighth term of an arithmetic series is twice the third term. The sum of the first eight terms are 39.Calculate the first term. Please help
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