Question 412077
The 8th term of an arithmetic sequence is 25 and the 20th term is -11. Find the first term of the sequence and the common difference and use those to write the general term.
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Equations:
a + 7d = 25
a + 19d=-11
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Subtract and solve for "d":
26d = 36
d = 18/13 (common difference)
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Solve for "a":
a + 7d = 25
a + 7(18/13) = 25
a + 126/13 = 325/13
a + 126/13 = 262/13
a = 199/13 (1st term)
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General term:
a(n) = 199/13 + (n-1)(18/13)
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Cheers,
Stan H.
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