Ques. for all

Prove that 100400 can be written as the sum of two squares of integers....!!

Such an easy one....... but a good one though.......!!

3 Answers

21
Arnab Kundu ·

please check if the question is corrert?
wont the no. be 100497???
because the theory is any no. 1 more than multiple of 4 can be expressed as a sum of two integer's squares..............

36
rahul ·

well @Arnab -> Ya u r right .....!! well i've discussed bout this type of questions earlier....

I remember it now....

If some one wants the answer then they can read it in the hidden area below....


Any integer is of the form 2k or 2k+1
Now, there are three cases
Remaneder if
. (even)2 + (odd)2
. (odd)2 + (odd)2
. (even)2 + (even)2
is divided by 4

so let's check out

case 1
(2k)2 + (2k + 1)2 = 4k2 + 4k2 + 4k + 1 = 8k2 + 4k + 1
which on division by 4 leaves remainder 1

case 2
(2k + 1)2 + (2k + 1)2 = 2(4K2 + 4K + 1) = 8K2 + 8K + 2, which on division by 4 leaves remainder 2

case 3
(2k)2 + (2k)2 = 8k2, which on division by 4 leaves remainder 0

So Conclusion, Sum of the squares of any two integers, on division by 4 leaves remainder 0,1,2

So le'ts check it on 100400, on division by 4 it leaves remainder = 0, so yes it can be written as the sum of two squares

Again, on 100497, on division by 4 it leaves remainder =1, so yes it can be written as the sum of two squares

And that's it....... Hope this was of some use to some of you

71
Vivek @ Born this Way ·

And that's it....... Hope this was of some use to some of you

Of course it is!

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