Which of the following represents the value of the series? cap s sub 28 is equal to the sum from k is equal to 1 to 28 of open paren 9 minus 4 close paren

The summand is the arithmetic sequence 9k − 4. Its first term is 9(1) − 4 = 5, and its 28th term is 9(28) − 4 = 248. The sum is the number of terms times the average of the first and last terms: 28(5 + 248)/2, which is choice D.

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