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4 votes
4 votes
For the arthritic sequence 5,9,13,17,21,... how many terms would you need to get to 129

User Greg Levenhagen
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1 Answer

20 votes
20 votes

9514 1404 393

Answer:

32

Explanation:

The first term is 5 and the common difference is 9-5=4, so the n-th term is ...

an = a1 +d(n -1)

an = 5 +4(n -1) = 4n +1

Then the term number for the term 129 is ...

129 = 4n +1 . . . . . put the given value in the formula

128 = 4n . . . . . . . subtract 1

32 = n . . . . . . . . . .divide by 4

The 32nd term is 129.

User Nghi Nguyen
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