Olympiad stuff

Here is a great problem for the olympiad pursuers -- as far as I think--
Ptove that every positive integer can be written as the sum of not more than 48 integers , each raised to the power 4 and zeroes are excluded.

10 Answers

1
Arshad ~Died~ ·

suppose we take 49 and we write it as
49=14+14+....so on 49 times then this proves to be wrong.....

1
Maths Musing ·

Extremely sorry , 1 is not allowed too.

1
Arshad ~Died~ ·

so now if we take
24 + 24 +........49 times= whatever dat integer value is then also this proves to be wrong...
i think this question is wrong....

39
Dr.House ·

question is wrong :O ?

1
Arshad ~Died~ ·

@soumya
i would really like to see how u proved it
:-D

1
Unicorn--- Extinct!! ·

Question is correct. I have seen this before. But the solution went over my head!!

1
Philip Calvert ·

arshad you are doing ulta.
read the question once more.

23
qwerty ·

i think the question wants us to prove that we require maximum only 48 integers each raised to power 4 , to express any other positive integer ..........is it correct ??

btw i dont understand why dey use very high language in questions .....
questions are asked to test a student's intellectual capability or their language skills ?? i m serious about it ..i hav gone thru many physics problems which will take 2 days to understand the grammar of d question and the answer requires no more than 2 seconds of thinking ...... LOL ...

1
Arshad ~Died~ ·

woah.....what a difficult way to state a question....
sorry soumya...i mistook it.....
:-(

1
Maths Musing ·

qwerty is correct. The solution is ----

(a+b)4 + (a-b)4 = a4 + 4a3b + 6a2b2 + 4ab3 + b4 + a4 - 4a3b + 6a2b2 - 4ab3 + b4
= 2a4 + 12a2b2 + b4

so, [(a+b)4 + (a-b)4] + [(a+c)4 + (a-c)4] + [(a+d)4 + (a-d)4] + [(b+c)4 + (b-c)4] + [(b+d)4 + (b-d)4] + [(c+d)4 + (c-d)4] = 6a4 + 6b4 + 6c4 + 6d4 + 12a2b2 + 12a2c2 + 12 a2d2 + 12b2c2 + 12b2d2 + 12c2d2
= 6 ( a2 + b2 + c2 + d2 )2

If you carefully see , then you will find that the l.h.s of the identity contains 12 integers in the form of fourth powers .
But each one of them can again be expressed in terms of different a,b,c,d in the form 6 x (the sum of squares of different a,b,c,d)2.
So each term in the l.h.s can be expressed with maximum of different 4 numbers each raised to the power 4.
[as (a2 + b2 +c2 +d2)2 contains 4 terms with powers 4.]
So r.h .s = 12 x maximum 4 different integers each raised to the power 4
or the initial number = 48 integers each raised to the power 4

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