anonymous one year ago what is s10 for 1+4+16+64+......?

1. anonymous

hai ganeshie

2. ganeshie8

hey!

3. anonymous

help? :P can i also have steps so i know wit I'm doing?

4. ganeshie8

lets see, do you notice any pattern in the given series ?

5. anonymous

ya multiply 4

6. ganeshie8

Right, $$S_{10}$$ means the sum of first $$10$$ terms : $S_{10} = 1 + 4 + 4^2 + 4^3+\cdots + 4^8 + 4^9$ just check if we have exactly $$10$$ terms in above sum

7. anonymous

._.

8. anonymous

so is there a formula or something? cause this is way too long

9. ganeshie8

Need more than two dots and a hyphen to continue assist you .-.

10. anonymous

._. thats all i got

11. anonymous

BRUH U DASHED OFF WHEN U COULDNT HELP ME?!!

12. anonymous

help :(

13. butterflydreamer

note: This is a geometric progression :) So, if you want to find the sum of the first 10 terms, you would use this formula: $S_n = \frac{ a(1-r)^n }{ 1-r }$ n = nth term, r = common ratio, a = first term

14. anonymous

Geometric progress question...

15. butterflydreamer

oops i typed it wrong. Give me a minute

16. butterflydreamer

*$S_n = \frac{ a(1-r^n) }{ 1-r }$

17. butterflydreamer

that is the sum formula LOL

18. anonymous

$a_n=a_1(r ^{n-1})$

19. anonymous

so if i use this i get $S10=\frac{ 1(1-4^2) }{ 1-4 }$

20. anonymous

5 and it doesnt make sense?

21. anonymous

?

22. butterflydreamer

how did you get the 4^2 part?

23. anonymous

he put it inside the parentheses instead of outside

24. anonymous

4^10

25. anonymous

SRRY

26. anonymous

caps

27. butterflydreamer

yes it should be 4^10 :) Nowwww, simplify

28. anonymous

349525?

29. butterflydreamer

excellent :)!

30. anonymous

yea...i initial thought it was asking for the 10th term lool

31. anonymous

YAY! THNX :3

32. anonymous

until i saw its S not a

33. butterflydreamer

no worriesss ^_^!