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#926 Help Me ! » Proof of squares » 2007-06-29 23:45:41

Identity
Replies: 4

Prove that the square of an odd number is of the form 8q + 1.

Let m = an odd number
All numbers can be represented in the form 4k ± 1.
Hence, m = 4k ± 1.
m² = (4k ± 1)² = 16k² ± 8k + 1 = 8k(2k ± 1) + 1

But what if you choose 2k ± 1? Won't that give the same answer?

m² = (2k ± 1)² = 4k² ± 4k + 1 = 4k(k ± 1) + 1

Huh? Now it's only of the form 4q + 1???

#927 Re: Help Me ! » PlusMinus » 2007-06-29 22:12:10

Uh...just one more question, how can ±x + ±x = 0?

#929 Re: Help Me ! » PlusMinus » 2007-06-29 21:43:09

Because by looking at the first equation, you know that you will square root both the top p and the bottom q. Can't this be directly written also as

? Because you have the choice to sqrt them separately?

#930 Re: Help Me ! » PlusMinus » 2007-06-29 21:40:20

Also, +-'s are a major headache when it comes to the distributive law! How is it supposed to work?

...

What happens if you multiply

by
... or
by
?

Also... is

????

#931 Help Me ! » PlusMinus » 2007-06-29 21:16:30

Identity
Replies: 10

I'm a bit confused about the +- sign.

If

Then

Do the +-'s cancel out or what???

If you have this, then multiply

to both sides, where does the +- go? Does it stay with the
or go to the other side?? yea im a bit confused

#932 Re: Guestbook » Unusually Quiet? » 2007-06-29 19:27:46

I think what's "cool" changes as you grow up. In Junior School, it's cool to be fascinated in sciences, in Mid school it's not cool to be smart, in High school smart people get to make fun of others.

#934 Re: Puzzles and Games » Primes » 2007-06-26 05:27:21

Let's just start at 67116436219957, shall we?

#935 Re: Help Me ! » Finding the relation » 2007-06-26 04:06:32

Hmm, i will have to mull over that...

In the meantime, I came up with this:



where

is the nth term in the first table I provided.

The proving is incomplete... but it kinda implies that

, so

It might work on the other table too... dunno, and it breaks down when you get into tricky relations

Can you please check / improve this thx:)

#936 Re: Puzzles and Games » What's going on? Crazy sequence » 2007-06-26 02:46:07

311311222113111231131112132112311321322112111312211312111322212311322113212221
132113213221133112132113311211131221121321131211132221123113112221131112311332111213211322211312113211

#937 Re: Help Me ! » Finding the relation » 2007-06-26 02:42:31

How is the first one obvious though? Is there a non-graphical way to do this? I think there probably is... we did something kinda similar in physics, but I can't get my mind around it.

#939 Help Me ! » Finding the relation » 2007-06-26 02:13:14

Identity
Replies: 7

a         1             2            3            4            5
b         3             0.75       0.33       1.875      0.12

what is the quickest and fastest way of finding the rule between relations like this???

and this

m         1             2           3            4              5       
n         7.2         5.09        4.16       3.6           3.22

They are pretty simple in that they will be only be in the form

, but the book gives this profusely long trial error 'draw graphs and see if it is a straight line' approach. Thx

#940 Re: Puzzles and Games » Primes » 2007-06-23 07:46:37

Nooooo too many in a single post!!!

223241

#941 Re: Puzzles and Games » Primes » 2007-06-22 20:52:34

47 - 四十七 (Chinese)

#943 Re: Maths Is Fun - Suggestions and Comments » What is a Function? » 2007-06-21 18:12:49

So if there is no

infront of the square root, it means it is positive?

#944 Re: Euler Avenue » GRE subject test » 2007-06-21 07:25:43

Oh I see, too bad the 'solve' command only gives 2 solutions >.<

#945 Dark Discussions at Cafe Infinity » Global Warming scenarios » 2007-06-21 07:18:55

Identity
Replies: 27

Global Warming? Will it happen? What are we going to do about it?

This guy breaks down the argument very simply by analysing a grid of scenarios, and his own argument is quite strong.

http://www.break.com/index/tough-to-argue.html

#946 Re: This is Cool » Microsoft Math 3.0?? » 2007-06-21 03:34:51

tsk tsk microsoft trying to rule the world again... as shocamefromebay said, it looks too much like a calculator.

#947 Re: Euler Avenue » GRE subject test » 2007-06-21 03:26:40

Ricky wrote:

Nope identity, you gotta add one more.

But how???

#948 Re: Dark Discussions at Cafe Infinity » Relative velocity (a physical demonstration) » 2007-06-20 04:48:58

Perhaps the ball merely retained some of its initial velocity. Using that kind of speed meter in the car can lead to major inaccuracies.

#949 Re: Euler Avenue » GRE subject test » 2007-06-20 04:29:05

Is the answer to 63

. All the other questions on the test are hard! You must have to be a polymath to do well on that.

#950 Re: Dark Discussions at Cafe Infinity » Relative velocity (a physical demonstration) » 2007-06-20 04:17:12

But it's impossible that it just drops to the ground, because first it must accelerate to 100kmh-¹, right?

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