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#326 Help Me ! » Check my proof guys » 2007-03-14 05:14:18

Stanley_Marsh
Replies: 9

Show that for each n we can find an n-digit number with all its digits odd which is divisible by 5^n.

Assume the a number 

can be divided by

In the n+1 case


Now we have to prove

because all digits have to be odd , then k must be odd, and
,

Let m be odd , then there will always be solution to k and

#327 Re: Help Me ! » Anyone knows this?? » 2007-03-13 20:25:38

The fourth one ,

which is not below 0 , so the value of the function will always increase ,such function contains no period.

#329 Re: Help Me ! » Anyone knows this?? » 2007-03-13 20:07:17

The first one, Let f(x)={x}={x+k} k must equally to any integers, the min period is 1
The second , let f(x)=cot(x+7)=cot(x+7+k) , since the period of cot is


then k=

#330 Re: Help Me ! » Anyone knows this?? » 2007-03-13 19:38:04

Here a method , assume k are their period. Check out whether the equation F(x)=F(x+k) has a constant solution for k for any x.

#331 Re: Help Me ! » solve this » 2007-03-12 14:52:40

It's a group of Equation or just two separate equations?

#332 Re: Help Me ! » A problem » 2007-03-11 14:00:13

I thought


and by wilson's theorem
if p is a prime
then get 

then I don't know what to do

#333 Help Me ! » A problem » 2007-03-11 13:51:48

Stanley_Marsh
Replies: 3

For

consider the rational number

Where

and   
are positive integers. Prove that if p is an odd prime , then the numberator
of
is divisible by p.

#334 Re: Help Me ! » Differential Equation Problem » 2007-03-11 13:32:34

I wanna learn Differential Eq too , That Website totally rocks~ thanks  JaneFairfax.

But it only has solutions , I wonder how they found those solutions.Need Proof

#335 Re: Help Me ! » Differential Equation Problem » 2007-03-11 13:30:00

  ,LOL , I just followed the steps on my formular book , and got that , no idea how to get it at all.

#336 Re: Help Me ! » sinusoidal wave speeds???? » 2007-03-10 06:10:09

speed = wave lengh / period (time)

#337 Re: Dark Discussions at Cafe Infinity » Any guidence? » 2007-03-10 05:59:03

And I wanna ask you guys are there any math test? I need to prove I am eligible for the university I am about to apply for.

#338 Dark Discussions at Cafe Infinity » Any guidence? » 2007-03-10 04:26:35

Stanley_Marsh
Replies: 1

I have been to San Francisco for only 2 month from China , and I haven't finnished high school yet , but I am 18 , 18 can't enter high school in California.I want to go to univeristy by taking test or stuff like that . I major in math and physics . Any good advice about test taking or university recommanding? thanks guys.

#339 Re: Help Me ! » Need to remember the formulae? » 2007-03-10 03:26:43

let give a percific example ,  (3.4) is above or below y=5x+6 ?  if you assume x=3 then y=5x3+6=21 ,21>4, that means the line is above the point.

#340 Re: Introductions » Deleted » 2007-03-10 02:31:44

Hi , Dan .  I am simply just an ameteur , and you are professional , you learn a lot , hope I got the time too lol~~

#341 Re: Help Me ! » in dire need of help » 2007-03-10 02:14:51

Oh right , the starting  temp , there should be some formula?

#342 Re: Help Me ! » please help » 2007-03-09 18:36:29

Give you a tip , you can divide the v into two v on x-axis and y-axis.
the v on y-axis describe the motion in height , and the x-axis in lenght.  Two motion are independent.

#343 Re: Help Me ! » in dire need of help » 2007-03-09 18:32:57

Here is my opinion , though I 've never learned about Temp, Pressure, Gas.   

If a water particle with 0 deg c encounter with a 100 deg c water particle , they will both become 50 deg c . The mass of the steam is 10 g and the mass of the ice is 50 g , imply that ice has 5 times particle that of the steam. So the final temp should be

#344 Re: Help Me ! » please help me on geometry » 2007-03-09 10:35:38

in certain shapes , sum of the angles equal to 180d , 270d, ..so on. does this help?

#345 Re: Help Me ! » math help » 2007-03-09 10:21:28

you don't  need to get v , you know that v/t=a , from the v=2t , divide both sides by t, you get  v/t=2 , thus a=2 , that's it

#346 Re: Help Me ! » math help » 2007-03-09 06:50:05

Okay ,

  a is the acceleration , then apply the Newton's law ,
Thus you get your answer

#347 Re: Help Me ! » Pls expand this for me » 2007-03-08 19:03:54

I just looked up some information for you , I haven't seriously learned the expansion.

#349 Re: Help Me ! » help needed » 2007-03-08 10:42:46

Stanley_Marsh wrote:

In Z17, 5^2>17 , therefore the solutions exist only above or equal to 5. Let X be the solution ,

solve this one .Oh...I forgot how to solve this equation....I am sure it can be solved.

I find some information about it but I am not sure how to operate.
As I stated above , all you have to do is to solve

is equivalent to finding a value y such that 


Pick a few small moduli m ,If  y mod m does not make 2+17y a quadratic residue of m ,then this value of y may be excluded,Furthermore, values of  y> 17/4 are never necessary.

This method is called Excludent ,by the way.

#350 Re: Help Me ! » Math Help » 2007-03-08 10:18:41

yeah, I realize that. , any more effective way?

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