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What is ∑n=18(3n−1) equal to?

 May 16, 2018

Hey Hev!


We can see this is an arithmetic sequence, 


It is obvious because the formula in the summation notation gives us the formula, 3n - 1 


We just need to find the sum of the 8 terms. 


To find the sum of an arithmetic sequence, we use the formula:


\(S_n=\frac{n}2(a_1+a_n)\), where \(S_n\) is the sum, n is the number of terms, a1 is the first term, and an is the last term.


We plug in the values of n into the formula, to find the term value. 


\(S_n=\frac82(2+23)=100\), that is your final answer. 


I hope this helped,



 May 16, 2018

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