## INeedHelpPlease? one year ago How to find nth term of the series,and therefore Sum of n terms?

$\Large S_n=\frac{1}{1.4} + \frac{1}{4.7} + \frac{1}{7.10}..n$

@hartnn

3. hartnn

n'th term 1/n(n+3)

but that doesn't match for n=3?

5. hartnn

|dw:1389456863526:dw| do this for every term

6. hartnn

yeah, 1/n(n+3) will not work,

7. hartnn

that "...n" implies thatere are total n terms ?

yep

9. hartnn

3n-2 3n+1

10. hartnn

1/ [ (3n-2)(3n+1)] this works ?

how did u think of that ? :|

works i guess

13. hartnn

easy difference of 3 so multiple of 3 1..4...7..are all 1 less than multiple of 3

14. hartnn

***two less than

15. hartnn

did u get what to do for each term ? partial fraction kind of thingi

how do i find Sn now? partial fraction?i remember it kinda - 1/3((3n-2)-(3n+1))/(3n-2)(3n-3) ?

17. hartnn

did u get what i did in the drawing ?

which drawing O_O

19. hartnn

if yes, do it for 2nd term and tell me what u get

why did u do that?

1/4=3/4?

22. hartnn

i'll correct it , wait

23. hartnn

|dw:1389457539226:dw|

24. hartnn

do the same thing for 2nd term, then 3rd term, and observe what happens, then you'll know why that was done

okay

26. hartnn

did you get your sum ?