We are given an arithmetic sequence $\{a_n\}$ with common difference $d = \frac{1}{2}$ and $a_{17} = 10$. We need to find the sum of the first 17 terms, $S_{17}$.

ArithmeticArithmetic SequencesSum of Arithmetic SeriesSequences and Series
2025/6/14

1. Problem Description

We are given an arithmetic sequence {an}\{a_n\} with common difference d=12d = \frac{1}{2} and a17=10a_{17} = 10. We need to find the sum of the first 17 terms, S17S_{17}.

2. Solution Steps

The general formula for the nn-th term of an arithmetic sequence is:
an=a1+(n1)da_n = a_1 + (n-1)d
We are given a17=10a_{17} = 10 and d=12d = \frac{1}{2}. We can use the formula to find a1a_1:
a17=a1+(171)da_{17} = a_1 + (17-1)d
10=a1+161210 = a_1 + 16 \cdot \frac{1}{2}
10=a1+810 = a_1 + 8
a1=108=2a_1 = 10 - 8 = 2
The formula for the sum of the first nn terms of an arithmetic sequence is:
Sn=n2(a1+an)S_n = \frac{n}{2}(a_1 + a_n)
We want to find S17S_{17}, so we have:
S17=172(a1+a17)S_{17} = \frac{17}{2}(a_1 + a_{17})
S17=172(2+10)S_{17} = \frac{17}{2}(2 + 10)
S17=172(12)S_{17} = \frac{17}{2}(12)
S17=176S_{17} = 17 \cdot 6
S17=102S_{17} = 102

3. Final Answer

The sum of the first 17 terms is
1
0

2. So the answer is (D).

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