1. anonymous

$\sum_{n=1}^{15} (2n+1)$

2. anonymous

there are a couple ways to do this

3. anonymous

Okay I need the simplest way because I'm not good with this.

4. anonymous

ok lets find the first term, which means replace $$n$$ by $$1$$ what do you get?

5. anonymous

3?

6. anonymous

if that is confusing too, let me know and i will show you lol no not "3?" just "3"

7. anonymous

I know it is just 3 I was asking if 3 was right.

8. anonymous

yeah $$2\times 1+1=3$$ ok now the top number is 15 so lets find the 15th term replace $$n$$ by $$15$$ and see what you get

9. anonymous

31

10. anonymous

ok good now there are 15 terms all together one formula you can use is $\huge \frac{n}{2}\left(a_1+a_n\right )$

11. anonymous

you computed $$a_1=3,a_{15}=31$$ and in this case $$n=15$$

12. anonymous

so do this $\frac{15}{2}(3+31)$

13. anonymous

15/2(33)

14. anonymous

add first, divide by 2 then multiply by 15

15. anonymous

you got that?

16. anonymous

I meant 34 my number buttons are acting up and no. I was just stating the equation.

17. anonymous

ok so now divide 34 by 2 then multiply the result by 15

18. anonymous

255

19. anonymous

you found the sount

20. anonymous

sound bingo yes good work

21. anonymous