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## #1 Re: Help Me ! » rationals and irrationals » 2006-12-26 06:13:55

oh thanx, didnt realise that

Happy Christmas Toast

## #2 Help Me ! » rationals and irrationals » 2006-12-26 04:40:40

Rose-Red
Replies: 2

Could u please prove by contradiction (discrete maths) that "if n is an irrational number and m is rational then n + m is irrational".

P.S. doing my revision for exam and stuck here

## #3 Re: Help Me ! » Discrete maths - characteristic functions » 2006-11-12 08:08:33

well that's a controversial topic I started. In any case, I don't care anymore cause it doesn't change anything in my task.

thanx guys

## #4 Re: Help Me ! » Discrete maths - characteristic functions » 2006-11-12 07:11:42

I thought there is 1 if the letter belongs to both set, and 0 if it belongs only to the set A. In this case. letters "a" and "e" both belong to sets A and B, so shouldn't there be 1 in: "If the letter is 'a', then the value is  0."?
Anyway, I understand that, but is this the way I have to describe it? Besides, is letter "y" a vowel too, in English?

And one more thing, thanx for your help

## #5 Help Me ! » Discrete maths - characteristic functions » 2006-11-09 23:54:31

Rose-Red
Replies: 10

Hi there,

Here is the question."Let A be the set of 26 letter of the alphabet. Desribe the characteristic function of the set of vowels."
Well the definition of characteristic function seems very simple and I tried to apply it to my question but I'm stuck. I guess I don't understand what exactly I need to do.
Could anyone help me out?

## #6 Re: Help Me ! » Simplification » 2006-10-25 19:42:16

Thanx mate, that's the answer I needed to get

## #7 Help Me ! » Simplification » 2006-10-25 07:02:42

Rose-Red
Replies: 3

Hello,

does anyone know how I could simplify this expression:

``(ar - ar² + ar³ - a)/(r-1)``

## #8 Re: Help Me ! » weird equation » 2006-01-08 09:38:31

OMG I've never hear of that O_O
Thank you, I'll try to understand that and maybe use it later

## #9 Re: Help Me ! » weird equation » 2006-01-08 09:32:15

but i dont understand how it is possible. I cant find any rule or formula that allows to do that

## #10 Re: Help Me ! » weird equation » 2006-01-08 09:20:59

thanx man, but I did it in another more complicated way.

x³-9-6x=0
(x³-27)+18-6x=0
(x-3)(x²+27x+27²)-6(x-3)=0
(x-3)(x²+27x+723)=0

x-3=0
x=3

and
x²+27x+723=0
D<0 no solutions

Could u explain me how you get this (x^2+3*x+3)?

## #11 Help Me ! » weird equation » 2006-01-08 09:08:04

Rose-Red
Replies: 6

Could someone help me with this?

x³=6x+9

It doesn't seem difficult, but my answer doesn't suit to the answer in the book

## #12 Re: Help Me ! » Simplify » 2006-01-06 10:54:31

yeah, maybe you're right.

## #13 Re: Help Me ! » Simplify » 2006-01-06 10:23:02

I also tried to do that but in quite different way. Still I couldnt get the right answer. That's what I got

## #14 Re: Help Me ! » Square roots! Ech... » 2006-01-06 10:00:04

oh, I knew I did it right, but just missed that slash

## #15 Re: Help Me ! » Simplify » 2006-01-06 09:59:01

Maybe someone could simplify this?

again, I need the whole solution, because the answer is at the end of the book

## #16 Re: Help Me ! » Simplify » 2006-01-05 21:53:46

or you simply can see a formula (a-b)(a+b)=a² - b² ; as a result (x-1)(x+1)=x²-1²
so x(x-1)(x+1)=x(x²-1²)=x³-x

## #17 Re: Help Me ! » Square roots! Ech... » 2006-01-05 09:57:30

Thanx alot, I've been solving this for the whole week. Now its very clear. Making 9 into 2²+√5² was very new for me. Learning everyday. Hehe

thanx again

## #18 Re: Help Me ! » Square roots! Ech... » 2006-01-05 09:47:28

hey this is weird.
I understand everything till that 'thin moment'
first of all what the '^' mean? is it multiplying or what?
then where did you get √((2^2+√5^2)