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#451 Re: Help Me ! » solution please » 2006-12-21 04:08:52

you can simply combine all of them together and do division .

#452 Re: Help Me ! » Rational and irrational » 2006-12-21 04:06:17

Actually , I misunderstood the definition of Irrational number , I though like 3.33333333333...... is also irrational , however I was wrong .lol

#453 Re: Help Me ! » Rational and irrational » 2006-12-21 04:01:16

the second one , let r be rational , x be irrational , r =a/b for some a,b(Z) ,
Assume rx rational , rx=c/d for some c , d

x=bc/ad , contradiction. Thanks Ricky.For helping me out~

#454 Help Me ! » Rational and irrational » 2006-12-19 21:37:54

Stanley_Marsh
Replies: 10

If r is rational number , x is irrational , how can I prove r+x and rx are irrational?


Should I consider this problem to be a Field and Set problem? Help me out~

#456 Re: Introductions » Hi everyone! » 2006-12-19 02:09:55

hehe , Actually , I am a Cantonese , part of Chinese you can say , and I am so in luv with South Park ~lol

#457 Re: Help Me ! » Another Physics Problem » 2006-12-19 02:01:07

the horizontal accelerations of two cubes are the same~ if regard the two as one , we have  a=p/29he large cube endures 25*(p/29)wton force , this force equals to the sum of the p force and the force the small one attributes . the interactiing force measured p-(25p/29)  ,   the friction = [p-(25p/29)]*0.71  when the friction equals to the gravity of the smalls one , it will be minimum ,  [p-(25p/29)]*0.71=4*9.8  , which p is around 400 N ,I dont know if I am correct lol~

#458 Re: Dark Discussions at Cafe Infinity » Languages; What Are Yours? » 2006-12-19 01:38:46

I am a Chinese ,to be more precise , I am a Cantonese speak both Mandarin and Cantonese of course~ ~lol ,  I am learning Engish ,Norwegian now ~

#459 Re: Help Me ! » need help (ALGEBRAIC EXPRESSION) » 2006-12-18 01:40:19

Using the x^2+1/x^2 =53   ,get  (x-1/x)^2=x^2+1/x^2 -2=53-2=51
then x-1/x =51^1/2

Using the x+1/x=9  , get  77


omg ....lol

#460 Re: Help Me ! » A problem » 2006-12-16 03:47:14

Lol~ it still seems a little bit abstract for me to comprehence ~, I am working on it ~

#461 Re: Help Me ! » A problem » 2006-12-15 02:30:40

Thanks a lot ! Though it will take time to digest , It's very helpful!

#462 Re: Help Me ! » inner product » 2006-12-14 17:32:35

I think you can draw a graph about it , 2L+M connect the two point of a parallelogram consists by M and 2L , knowing the length of 2L , and 2L+M ,and the angle , use geometry to solve it

#463 Re: Help Me ! » A problem » 2006-12-14 17:07:16

Thanks , I think I have got a clue now ,  I am weak at the part about "mod" , by the way,Ricky,do you have any website that talks about mod , , Thanks

#464 Introductions » Hi everyone! » 2006-12-13 14:06:14

Stanley_Marsh
Replies: 32

I am a high school student ,who seeks help in the forum . I am 18  , I love maths and physics.

#465 Help Me ! » A problem » 2006-12-13 13:48:19

Stanley_Marsh
Replies: 8

I am trying to prove the set E={4n-1 , n=1,2,3,4....} contains infinite prime numbers.

odd numbers can be written as D={2n-1 , n=1,2,3.4} , E is bounded in D , D is infinite set , and so is E.
Prime numbers besides 2 , can only be divided by themselves and 1 , so Prim numbers besides 2 are odds
And the set A consists of Prime numbers(besides 2) is infinite , but How can I prove the intersection of A and E is infinite?
and How can I prove D has all the elements of E , though it's so obvious.

#466 Re: Help Me ! » Locus » 2006-12-13 13:33:26

I think you sould draw two circles , with the radius 4 m, and 3 m, then the intersection of the two is what you need

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