What is ∑n=18(3n−1) equal to?

Hev123  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,



GYanggg  May 16, 2018

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