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I found pic related in a book about problems in number theory,

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I found pic related in a book about problems in number theory, in the section of diphantine equations. It is so different from other problems and I am confused. What is the point of the problem?

Am I supposed to get the 5th power of all those numbers, add them up and then find the 5th root or is there some kind of trick meant to be used here?

I mean, I am sure that I could do it by brute force if given enough time but that doesn't feel like mathematics. There must be some trick, right?
>>
>>8669064
144
>>
>>8669087
I know the answer. But I am wondering what they expect me to do to get it.
>>
>>8669090
Galois Theory maybe ?
>>
It's clear that
133 < n < 4^(1/5) * 133 < 176

The last digit of n can be found easily by considering the equation modulo 10.
n^5 = 3^5 + 0^5 + 4^5 + 7^5 (mod 10)
= 4 (mod 10)
Which means that n^5 and therefore n has 4 as the last digit.

So you only have to test n=134, 144, 154, 164, 174.

It turns out that n=144 works.
>>
>>8669090
But it takes like 0.01sec to "bruteforce" (it's a simple exponentiation algorithm which is standard in any language today).
I'd just type that in python if i'd really have to solve it. Otherwise I'd say quintic function.
>>
>>8669095
The book is in 「Elementary」Number Theory. I doubt that they would make you use Galois Theory.
>>
>>8669100
>But it takes like 0.01sec to "bruteforce"

It is meant to be a pen and paper problem. The objective is to not bruteforce it. Like >>8669099 does.

I simply did not know how.

>>8669099
>133 < n < 4^(1/5) * 133 < 176

How do you know this?
>>
Look at the equation modulo 2:
n^5 = 0 (mod 2)
n = 0 (mod 2)
Look at the equation modulo 3:
n^5 = 0 (mod 3)
n = 0 (mod 3)
Look at the equation modulo 5:
n^5 = 4 (mod 5)
n = 4 (mod 5)
Look at the equation modulo 7:
n^5 = 2 (mod 7)
n = 4 (mod 7)

The Chinese Reminder theorem says that
n = 144 (mod 210)
for an integer k.

So n must be 144.
>>
>>8669111
>How do you know this?
133^5 < 133^5 + 110^5 + 84^5 + 27^5 < 4 * 133^5
>>
>>8669064
n needs to be larger than 133, and be congruent to 4 modulo 5.
Thread posts: 11
Thread images: 1


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