Question

last minute help

Answer 1

what's up?

Answer 2

find sum upto n terms 8,88,888,8888.................

Answer 3

Help help help.

Answer 4

I like to help.

Answer 5

Me too.

Answer 6

Is it very hard ?

Answer 7

more qns in que

Answer 8

lol

Answer 9

after this next qn

Answer 10

what have you tried in this problem ?

Answer 11

taking 8 common

Answer 12

and ?

Answer 13

its all about GP
a= 8
r= 88/8=11
sum(n)= 8(11^n -1)
----------
10

Answer 14

hey dashini i dont think r is 11

Answer 15

This not a geometric progression

Answer 16

ya

Answer 17

this question does involve a geometric series though (its hiding)

Answer 18

how?

Answer 19

The nth term is given by \( T_n=\large \frac{8\times(10^n-1)}{9} \)

Answer 20

its a linear recursive function a(r+1) = 10*a(r) + 8

Answer 21

i need sm upto n

Answer 22

Dhashni??? come to my post!

Answer 23

sum

Answer 24

something for which you should try using your head first ? :P

Answer 25

\[8+88+888+8888+\cdots+888\ldots 88\]\[=8(1+11+111+1111+\ldots+111\ldots 11)\]

1111...111 is the same as:\[1+10+100+\ldots+ 10^{n-1}=\frac{10^n-1}{9}\]

Answer 26

hey joe u shud write n instead of 1

Answer 27

isnt it???

Answer 28

nopes joe wrote right.

Answer 29

so like others have said, you are looking for:\[\sum_{n=0}^n8\cdot \frac{10^n-1}{9}\]

Answer 30

8/9(10n\[8/9\ 10n+100-10^{n}\10]\]

Answer 31

so wat is final answr?

Answer 32

\( \sum_{k=0}^n8\cdot \frac{10^k-1}{9} = \frac{8}{81} 10(10^n-1)-9n \)

Answer 33

that should be pretty straight forward to calculate. pull out the 8/9, and split of other part with addition.

Answer 34

*substraction i mean.

Answer 35

btw joe, \( \sum_{n=0}^n \) is ambiguous :P

Answer 36

yeah, i just noticed lolol >.<

Answer 37

ya wt shud i giv as final amnswr??

Answer 38

hehe :D

Answer 39

should have made my dummy variables i instead.

Answer 40

give whatever you get when you calculate the sum.

Answer 41

next qn :what is slope of x/a +y/b=1

Answer 42

b/a

Answer 43

hw u got that???

Answer 44

missing the negative.

Answer 45

-b/a

Answer 46

ya.. it's -b/a

Answer 47

\[4(n(n+1)) - 8/9 *n +8/81 * (1-10^n)\]

Answer 48

convert the equation into slope form..

Answer 49

two ways of getting that slope

write it in the form y=mx+C

Answer 50

or the slope of a line ax+by=c is -a/b remember that

Answer 51

you in which grade?

Answer 52

next qn:::cos20cos40cos80=1/8 prove this!!

Answer 53

me? :P

Answer 54

Have you considered trying this elementary problems yourself first ?

Answer 55

yea aravind try it yourself

Answer 56

use the formula ....cosx * cosy = [cos(x+y) +cos(x-y)]/2

Answer 57

\[\cos \theta * \cos(60-\theta)*\cos(60+\theta)=\cos3\theta\]

Answer 58

then how 1/8???

Answer 59

as they say we given you all the data required to find the solution give it a try.

Answer 60

i am getting 1/2 :(((

Answer 61

you saw him now ffm? he is here from past half hour

Answer 62

it's 1/4cos60..