# A Maths Question

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17 years ago
#21
(Original post by Fermat)
Here's a solution here.

I see a slight problem:

1+r^2+r^4+r^6 =/= (1+r)(1+r^4).
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17 years ago
#22
(Original post by Ralfskini)
I see a slight problem:

1+r^2+r^4+r^6 =/= (1+r)(1+r^4).
Its just a typo - it should be 1 + r² + r³ + r^6 = (1 + r²)(1 + r^4)

Also Fermat I think the problem is that without knowledge or a hint to use the substitution u = r + 1/r the polynomial has no obvious roots so is hard to factorise and solve for r, so Katie thinks there must be an alternative method that doesn't require this change of variable
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17 years ago
#23
(Original post by It'sPhil...)
Its just a typo - it should be 1 + r² + r³ + r^6 = (1 + r²)(1 + r^4)

Also Fermat I think the problem is that without knowledge or a hint to use the substitution u = r + 1/r the polynomial has no obvious roots so is hard to factorise and solve for r, so Katie thinks there must be an alternative method that doesn't require this change of variable
Yes, that is a problem. Unfortuanetely I have little idea of what maths level people are at!
Using that substitution is about the only way I can see of solving it?
High power polynomials are usually solved by some method which will reduce the power.
Spotting a factor in the polynonmial is about the only other way I can think it might be solved.

Edit: In an analytic way that is.
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#24
(Original post by Fermat)
Yes, that is a problem. Unfortuanetely I have little idea of what maths level people are at!
Using that substitution is about the only way I can see of solving it?
High power polynomials are usually solved by some method which will reduce the power.
Spotting a factor in the polynonmial is about the only other way I can think it might be solved.
yep I fear you may be right.
The solutions I have seen all contain that substitution. But, as I keep saying, I can't imagine that substituion would be obvious to a GCSE student so that's why I thought, considering its meant to be accessible to that age group, there must be an alternative method. But no-one I know has yet found it. Perhaps it doesn't exist.
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17 years ago
#25
I think I know how this problem could be solved using very basic maths. It does involve using all possible combinations, but there aren't many.
A] We want a sequence of four whole numbers, n, nr, nrr, nrrr {I've not worked out how to enter maths notation on this thing, so apologies], with the highest number below 36.
B]Either one or three of the numbers must be odd.
C] (nrrr+nr)-(nrr+n)=13.
n and r must both be negative, but that doesn't matter for calculation.
There can't be many ratios that produce four whole numbers below 36, so apply the obvious, r=2. This gives n=1 or n=3, and neither fulfils condition C.
The next simplest ratio is r=3/2.
This gives the sequence n, 3n/2, 9n/4, 27n/8, which in turn gives 8, 12, 18, 27. Squares are 64, 144, 324, 729
This fulfils condition C and the squares of these numbers equal 1261.
Both n and r are negative, so the sequence is -8, 12,-18, 27 and r is -3/2.
In fact, the only geometrical progression ratios that can produce four whole numbers below 36 are 2 or 3/2.
I didn't time myself on this, but it took a lot less time than typing this did- I think that while younger students go for a formula or a calculator first, people of my age who were drilled through mental arithmetic, probably produce the answer without much thought: I "knew" almost at once that the sequence above was right: i had to spend much longer showing it.
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17 years ago
#26
Easy crap,

xsquare + ysquare = 1256
x + y = 13

Solve the simultaneous equation, This is under GCSE stuff
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17 years ago
#27
(Original post by Katie Heskins)
note the fact that the method they used was Laurent poly's.
Did you read my solution? It may have used somthing called laurent polynomials, but that would have been unintentional, I do not have a clue what they are!
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17 years ago
#28
(Original post by Godsize)
Easy crap,

xsquare + ysquare = 1256
x + y = 13

Solve the simultaneous equation, This is under GCSE stuff
idiot
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#29
(Original post by mikesgt2)
Did you read my solution? It may have used somthing called laurent polynomials, but that would have been unintentional, I do not have a clue what they are!
yes I did and yes it did! Using the substitution is great...I just wasn't convinced that it was the most obvious way. Apparently it was! Cheers, Katie
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#30
(Original post by Godsize)
Easy crap,

xsquare + ysquare = 1256
x + y = 13

Solve the simultaneous equation, This is under GCSE stuff
Bless him
0
17 years ago
#31
Just because you bloody pieces of **** cant uynderstand this it isnt my problem. Look up your maths books you rancorous coiffured old sows

Solve this and you'll get the answer.
xsquare + ysquare = 1261
x + y = 13

Now I have no time for games.
0
17 years ago
#32
(Original post by Godsize)
Just because you bloody pieces of **** cant uynderstand this it isnt my problem. Look up your maths books you rancorous coiffured old sows

Solve this and you'll get the answer.
xsquare + ysquare = 1261
x + y = 13

Now I have no time for games.
Okay. Firstly there are four numbers. As far as I am aware, using x and y and finding the solutions would give you two numbers. And... I can't really be bothered to say anything else.
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17 years ago
#33
(Original post by Godsize)
Just because you bloody pieces of **** cant uynderstand this it isnt my problem. Look up your maths books you rancorous coiffured old sows

Solve this and you'll get the answer.
xsquare + ysquare = 1261
x + y = 13

Now I have no time for games.
did you read the other solutions to this question?
have you actually read the question?
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17 years ago
#34
Solve the simultaneous equations first. You'll get two quadtratic equations solve those and you get FOUR FOUR FOUR FOUR FOUR answers...

And stop giving me those bad rep points, I had 8 now I have 4....
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17 years ago
#35
(Original post by Godsize)
Solve the simultaneous equations first. You'll get two quadtratic equations solve those and you get FOUR FOUR FOUR FOUR FOUR answers...

And stop giving me those bad rep points, I had 8 now I have 4....
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17 years ago
#36
I've got them, And whoever is giving me the bad reputation:

May the air make you sick and thuder strike your bones, May you fall into the deepest of the abyss and burn in thy purest form. Make food make you weak and breathing cause you death.

Mustaine sez,
Bye
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17 years ago
#37
I have been waiting for you to prove your claims. I can't do it. Show me.
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17 years ago
#38
I cant Its too long a method, it also uses the quadratic equation anyhow,
You get a quadratic equation from subtituting equation x, You solve it and then place the values in the other equation (You have two from the quad eq.) You get two more values which are the answers, I made my brother (who's a engineer) solve it he said it was correct. Now give me back those repuatations~!
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17 years ago
#39
You ain't getting your reps back until you do it.
0
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