Precalculus Examples

$\sum_{k = 1}^{7} {(- 1)}^{k} (11 k)$

Step 1

Factor $11$ out of the summation.

$(11) \sum_{k = 1}^{7} {(- 1)}^{k} k$

Step 2

Expand the series for each value of $k$ .

${(- 1)}^{1} (11 \cdot 1) + {(- 1)}^{2} (11 \cdot 2) + {(- 1)}^{3} (11 \cdot 3) + \dots + {(- 1)}^{7} (11 \cdot 7)$

Step 3

Simplify the expanded form.

$- 44$