Answer:
832
Step-by-step explanation:
It can be helpful to write a few of the first terms. You will also need to know the last term of the sum.
For n=1, the first term in the sum is 2·1+5 = 7.
For n=2, the next term in the sum is 2·2+5 = 9.
For n=3, the next term is 2·3+5 = 11.
So, this sum is of the arithmetic sequence 7, 9, 11, ....
The last term in the sequence is 2·26+5 = 57.
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The average term in the series is the average of the first and last terms, so is ...
(7 +57)/2 = 32
The sum of the terms of an arithmetic sequence is the average term (32) multiplied by the number of terms (26).
Your sum is ...
sum = (32)(26) = 832
