[Macluawn]

x=0.(9)
10x = 9.(9)
10x-x = 9.(9) - 0.(9)
9x = 9
x = 1 = 0.(9)

le probleme, math people?

[Ash.]

I confused a math teacher by doing that - it was quite funny because I proved him wrong, after about a 30 minute debate about that!

[[MM]IKKE]

Quote:

Originally Posted by Macluawn x=0.(9) 10x = 9.(9) 10x-x = 9.(9) - 0.(9) 9x = 9 x = 1 = 0.(9) le probleme, math people?

What's this supposed to mean? If you want to prove it wrong, look at step 2: 10x = 9.9? If you define x as 0.9, then that's 9.0...

[Macluawn]

0.(9) = 0.999999999999...
it just means, that the number nine is repeating forever.

[Mauzen]

Ye good ol' problem, also was a popular topic during my physics lessons back at school.
0.(9) is indeed = 1, there are a lot of ways to proof that. I really like your solution, havent seen it that way before I think. However, thats the most simple one that comes up to my mind:

Код:

1/9 = 0.(1)          | x9
1 = 9/9 = 0.(9)

edit: +rep for a math topic finally

[[MM]IKKE]

Quote:

Originally Posted by Macluawn 0.(9) = 0.999999999999... it just means, that the number nine is repeating forever.

Oh, I know what it means now. Never seen that notation before tbh, we just write 0.99...And yes it's true, countless ways to prove them ( http://en.wikipedia.org/wiki/0.999... ), yours is included as well.

I like this one:

Quote:

has the limit 0. Considering the nth term of the sequence, for n=0,1,2,..., it must therefore be shown tha