SOLUTION: what is the sum of the first 4 terms of the arithemetic sequence in which the 6th term is 8 and the 10th term is 13

Question 368097: what is the sum of the first 4 terms of the arithemetic sequence in which the 6th term is 8 and the 10th term is 13
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
what is the sum of the first 4 terms of the arithemetic sequence in which the 6th term is 8 and the 10th term is 13
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a(6) = a(1) + 5d = 8
a(10)= a(1) +12d = 13
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Subtract the 1st line from the bottom:
7d = 5
d = 5/7
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Substitute for d and solve for a(1):
a(1) + 5(5/7) = 8
a(1) = 8-25/7
a(1) = 31/7
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Sum of the 1st 4 terms = ?
a(4) = (31/7) + 3(5/7) = 46/7
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S(4) = (4/2)(1st + 4th)
S(4) = 2((31/7)+(46/7)) = 2(77/7) = 22
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Cheers,
Stan H.

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