Asked by ryan
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
Answers
Answered by
Scott
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
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
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