Question

write the following sum using sigma notation.
$7 - \frac{7}{2} + \frac{7}{3} - \frac{7}{4} + \cdots - \frac{7}{46}$

Explanation:

Step1: Identify pattern of terms

Each term has form $(-1)^{n+1}\frac{7}{n}$

Step2: Define index range

$n$ starts at 1, ends at 46

Step3: Write sigma notation

Sum is $\sum_{n=1}^{46} (-1)^{n+1}\frac{7}{n}$

Answer:

$\sum_{n=1}^{46} (-1)^{n+1}\frac{7}{n}$