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#401 Re: Help Me ! » without the calculater » 2007-01-20 10:58:30

25x3=75
Sin3a= 3sina - 4(sina^3) after simplification(don't know if I am correct) , then just solve the equation.but how to solve it? lol.

#402 Help Me ! » Give you guys some exercise,lol » 2007-01-20 10:54:21

Stanley_Marsh
Replies: 6

Find the sum of  1x2x3+2x3x4+3x4x5............


  Find the formula for  the sequence 2A(n-1) + An = 2^n

A(n-1) and An represent the sequence

#403 Re: Help Me ! » Factorising Polynomials » 2007-01-20 10:49:03

x^4+4=x^4+(4x^2)+4-(4x^2) =  (x^2+2)^2-(4x^2) = (x^2-2*x+2)*(x^2+2*x+2)

you can use 0=-x+x ,this kind of idea to do it

#404 Re: Help Me ! » Elliptic... » 2007-01-20 10:38:24

Yeah, I been reading books about number theory recently , but I am a newbie to it , still struggling with group theory . You can post it out , I'll try to comprehence it ,lol.  P.S another question , how to apply imaginary number to prove certain problem , I mean how to consider using it?

#405 Re: Help Me ! » Find a solution for the equation » 2007-01-17 12:27:51

divide both side by 4 ,    we have 3/4x+y=3 , then x must be in this form of integer , x=4n ,n can be 1,2,3,4,5....... , then the equation becomes 3n+y=3 ,  n and y can be anything thing ~infinte solution.

#406 Re: Help Me ! » A Train........... » 2007-01-17 12:23:14

average speed v=s/t , s= bridge length+Train length (because it starts at one end of the bridge , when its tail pass over the other end ,we say it has gone through the bridge. so...

#408 Re: Help Me ! » Elliptic... » 2007-01-17 12:17:45

I am working on it ,  I tried when x=k ,y=k+1, no solution , x=k y=k+2 , no soltution , when x=k,y=k+3 one solution ,  then use induction on n , assume x=k , y=k+n , n>3 contains no solution. then if y=k+n+1 can be proved to contain no solution ,it's done , but I have difficulty in working on the last step.

#409 Re: Help Me ! » Elliptic... » 2007-01-17 12:13:41

Sorrri , my bad,  The solutions must be integers ,  This kind of equations are called elliptic curves. Solve this can solve a problem which Fermat once challenged other two mathematicians , noted that  26 is between 25 , 27 , 25=5^2 , 27=3^3 ,  prove that 26 is the only number which lies between a square and a cube.

#410 Help Me ! » Elliptic... » 2007-01-13 10:12:56

Stanley_Marsh
Replies: 12

Prove that  y^2=x^3 - 2 only has one solution.

#411 Re: Introductions » Hi again » 2007-01-07 11:21:05

Yah , I move with  my family .  I haven't got a computer yet .I am in a library.

#412 Help Me ! » asking for a formula » 2007-01-07 11:19:56

Stanley_Marsh
Replies: 2

Have any mathematician created a formula to determine the approximate value of n!

#413 Help Me ! » Help arrangements » 2007-01-07 11:17:51

Stanley_Marsh
Replies: 5

I was just wondering How many arrangements can be made to form a 9x9 grid Sudoku?

#414 Help Me ! » Help » 2007-01-07 11:14:45

Stanley_Marsh
Replies: 1

I realized that 16^2+15^2=481=13x37

Can't help asking :how to tell m^2+n^2 can be divided by x or y , when (m^2,n^2)=1 ,(m^2,x)=1
(n^2,x)=1 , (m^2,y)=1 ,(n^2,y)=1 . ?

#415 Re: Help Me ! » Integers » 2007-01-07 11:11:02

Very interesting question!Pity that I can seldom be online now , but  I have thought about it for hours , This is what I get :
15a + 16b =m^2   16a - 15b =n^2

a=14911 b=481 n=m=481

I don't know if it's right

after substitution of b ,  I get  a=(15m^2+16n^2)/481
then I thought a can only be an integer when m^2=481^2=n^2 .so.....lol~

#416 Introductions » Hi again » 2006-12-28 08:00:14

Stanley_Marsh
Replies: 14

I have moved to California , I have just arrived , so many stuffs are not settled , see you guys soon.

#419 Re: Help Me ! » A spooky discovery » 2006-12-23 13:02:49

And to how I get that , I get to find my notebook , it's been a long time .

#420 Re: Help Me ! » A spooky discovery » 2006-12-23 12:58:18

OMg , Thank you for solving my mystery! I get this from a  x^2+bx+c=0 equation , the determinant of root  b^2-4c . I think I see now .hehe

#421 Re: Introductions » Hi » 2006-12-23 06:18:23

Kewl , Jeg elsker Norge ! Norge er veldig gode!  Jeg vi gjerne reise til Norge ! Og jeg kommer fra China.Mitt navn er Dalron.
 
Welcome! Welcome! Nice to meet you~ lol , I am so in love with Norway.

#422 Re: Introductions » Hello everybody » 2006-12-23 06:12:12

coolcat23 wrote:

Who likes toast in milk?

Toast in milk actually pretty good, ,Clean toast will be quite dry I think

And Congrats ,Toast! , This is surely an awesome website~hehe

#423 Re: Introductions » Hi everyone! » 2006-12-23 06:08:50

George,Y wrote:

Hi I am Chinese. Nice meeting you!

Nice to meet you too, George!

#424 Re: Introductions » Hi everyone! » 2006-12-23 06:07:46

Thanks , I want to enhance my skill from helping and asking questions ,hehe

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