If an = (-1)n/2n-1, then a4 = ?
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Correct Answer: Option C
Explanation:
Given the sequence \( a_n = \frac{(-1)^n}{2n - 1} \), we need to find \( a_4 \).
1. Substitute \( n = 4 \) into the formula:
\[
a_4 = \frac{(-1)^4}{2 \cdot 4 - 1}
\]
2. Calculate \( (-1)^4 \):
\[
(-1)^4 = 1
\]
3. Calculate \( 2 \cdot 4 - 1 \):
\[
2 \cdot 4 - 1 = 8 - 1 = 7
\]
4. Substitute these values into the formula:
\[
a_4 = \frac{1}{7}
\]
Thus, \( a_4 = \frac{1}{7} \).
The correct answer is:
C. 1/7
Given the sequence \( a_n = \frac{(-1)^n}{2n - 1} \), we need to find \( a_4 \).
1. Substitute \( n = 4 \) into the formula:
\[
a_4 = \frac{(-1)^4}{2 \cdot 4 - 1}
\]
2. Calculate \( (-1)^4 \):
\[
(-1)^4 = 1
\]
3. Calculate \( 2 \cdot 4 - 1 \):
\[
2 \cdot 4 - 1 = 8 - 1 = 7
\]
4. Substitute these values into the formula:
\[
a_4 = \frac{1}{7}
\]
Thus, \( a_4 = \frac{1}{7} \).
The correct answer is:
C. 1/7