SOLUTION: Consider the arithmetic sequence that begins with the numbers 15 and 21. What is the 10th number in this sequence?

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Question 753041: Consider the arithmetic sequence that begins with the numbers 15 and 21. What is the 10th number in this sequence?
Answer by reviewermath(1029) About Me  (Show Source):
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Q:
Consider the arithmetic sequence that begins with the numbers 15 and 21. What is the 10th number in this sequence?
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A:
First term: a%5B1%5D = 15
Common difference, d = 21 - 15 = 6
nth term: a%5Bn%5D = a%5B1%5D+%2B+%28n+-+1%29d
= 15+%2B+%28n+-+1%29%286%29
= 6n+%2B+9
10th term: a%5B10%5D = 6(10) + 9 = highlight%2869%29