SOLUTION: Find the 10th term of an arithmetic sequence whose 5th term is 1.25 and whose 15th term is 18.

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Question 1039671: Find the 10th term of an arithmetic sequence whose 5th term is 1.25 and whose 15th term is 18.
Answer by Fombitz(32388) About Me  (Show Source):
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a%5B5%5D=a%5B0%5D%2B%285-1%29d=1.25
1.a%5B0%5D%2B4d=1.25
.
.
a%5B15%5D=a%5B0%5D%2B%2815-1%29d=18
2.a%5B0%5D%2B14d=18
Subtracting 1 from 2,
a%5B0%5D%2B14d-a%5B0%5D-4d=18-1.25
10d=16.75
d=1.675
and
a%5B0%5D%2B4%281.675%29=1.25
a%5B0%5D=-5.45
So then,
a%5B10%5D=-5.45%2B%2810-1%29%281.675%29
a%5B10%5D=9.625