Question

Summation help please

Answer 1

\[\large \sum_{k=5}^{10}-5k=-5\sum_{k=5}^{10}k=-5(5+6+7+8+9+10)\]

Or you can do:
\[\large \sum_{k=5}^{10}-5k=-5\sum_{k=5}^{10}k=-5\left(\sum_{k=1}^{10}k-\sum_{k=1}^{4}k\right)\]

and use the formula:
\[\large \sum_{k=1}^nk=\frac{n(n+1)}{2} \]

Answer 2

does in all add up to -225?

Answer 3

yes :)

Answer 4

C: yey. but for what it is asking. What would I put in the blank