jesusfreak 3 years ago Expand the series and evaluate: Enter your answer as the following example: -1-2-3-4-5-6=-21 sum_(k=5)^10(-5k)

1. amistre64

whats your best effort give us?

2. amistre64

seeing this done a few times should give you an idea that we can build upon

3. jesusfreak

Ok @amistre64, please leave me alone

4. amistre64

ok, but good luck with it all :)

5. jesusfreak

6. amistre64

im willing to help, but ....

7. jesusfreak

But what?

8. amistre64

9. jesusfreak

I want help I just don't want to be criticized

10. amistre64

noones criticizing you. I just need to know how much you know on this subject.

11. amistre64

does the notation make sense for starters.

12. amistre64

$\sum_{k=5}^{10}$is a good place to start

13. jesusfreak

I know nothing

14. amistre64

then this might take a bit. It is simple enough tho. the symbol: $$\sum$$ is a greek letter for "S" and indicated that we are going to be adding up stuff

15. amistre64

the number on the bottom tells us where we start at; and the number on top tells us where we end at: in this case we start with k=5 and end with k=10

16. jesusfreak

ok

17. amistre64

i like to write it out to begin with like this: k : rule ------- 5 : -5k = -5(5) = -25 6 : -5k = -5(6) = -30 7 : -5k = -5(7) = -35 8 : -5k = -5(8) = -40 9 : -5k = -5(9) = -45 10: -5k = -5(10)= -50 does this make sense so far?

18. amistre64

$\sum_{First}^{Last}(rule)$ using the rule, and stepping thru the numbers from first to last, we can generate all the numbers that are needed to be added up.