Question

What is the partial sum of ?

Answer 1

\[\sum_{i=10}^{25} -2-8i\]

Answer 2

Break that up to
\[-2\ \sum_{i=10}^{25}\ 1 \ \ \ \ -8\sum_{i=10}^{25} i\]
Does that help?

Answer 3

no

Answer 4

Do you know how to do the first summation:
\[\sum_{i=10}^{25}\ 1 \ \]

Answer 5

This summation is the number of items between i=10 and i=25 (inclusively).