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17. Write a function rule for the following arithmetic sequence and use it to find the 250th term. Show your work.
−3, 1, 5, 9, ….
Function Rule: Determining 250th term:

User Viacheslav
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1 Answer

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First check the difference between terms:


\{1-(-3),5-1,9-5,\ldots\}=\{4,4,4,\ldots\}

So every term differs by 4. The first term in the sequence is
a_1=-3. Recursively, the sequence is given by


\begin{cases}a_1=-3\\a_n=a_(n-1)+4&\text{for }n>1\end{cases}

Then


a_2=a_1+4


a_3=a_2+4=a_1+4(2)


a_4=a_3+4=a_1+4(3)

and so on, with the general rule


a_n=a_1+4(n-1)\implies a_n=4n-7

Then the 250th term of the sequence would be


a_(250)=4(250)-7=993

User John Channing
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