Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

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oh thanx, didnt realise that

Happy Christmas Toast

**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

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

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

**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?

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

**Rose-Red**- Replies: 3

Hello,

does anyone know how I could simplify this expression:

`(ar - ar² + ar³ - a)/(r-1)`

OMG I've never hear of that O_O

Thank you, I'll try to understand that and maybe use it later

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

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

Now the answer is correct.

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

**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

yeah, maybe you're right.

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

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

Maybe someone could simplify this?

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

so x(x-1)(x+1)=x(x²-1²)=x³-x

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

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)

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