Find the number of integer solution(s) to the equation x 2 + y 2 + z 2 = 2 0 1 6 .
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A programming approach, which gives the 1 8 positive triples, and then we can think of the -ve and multiply by 8.
in which class you r ? @Aditya Raut
Used the same method.You Will get exact triplets if you use intial value of i,j,k<=-45.
Exactly the same!
Exactly the same but I was wondering if there is a generating function solution too.
The generating function solution would be to try and find the coefficient of X 2 0 1 6 in ( X 0 + 2 X 1 + 2 X 4 + 2 X 9 + … ) 3 . Unfortunately, there is no simply way to simplify the expression (that I know of), so we're back to square 1.
This sum is expressible in terms of the Jacobi theta function , but I'm not sure that helps at all.
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First of all, note that 2 0 1 6 ≡ 0 ( m o d 4 ) implies that none of x , y , z is odd.
Because if any out of x , y , z is odd, x 2 , y 2 , z 2 will correspondingly be congruent to 1 ( m o d 4 ) , and no combination of 3 or less 1s will give a number divisible by 4.
Hence we conclude 2 ∣ x , 2 ∣ b , 2 ∣ c
We can say a = 2 x , b = 2 y , c = 2 z , and number of solutions of a 2 + b 2 + c 2 = 4 2 0 1 6 will be same as of original equation.
a 2 + b 2 + c 2 = 5 0 4 .
Now because 4 ∣ 5 0 4 , we conclude that again all of a , b , c are even.
So now problem reduces to integer solutions of j 2 + k 2 + l 2 = 1 2 6
As 4 ∤ 1 2 6 , we conclude that exactly 2 out of j , k , l are odd . And, the original numbers x , y , z are basically 4 j , 4 k , 4 l .
For simplicity, first let's find positive integer solutions such that a ≤ b ≤ c .
Now by observation, we have only the following solutions
( 1 , 2 , 1 1 ) ( 1 , 5 , 1 0 ) ( 3 , 6 , 9 )
For ordered triples, there will be 3 × 3 ! of these solutions.
Now as we want integer solutions, negatives would work too! Each of the 3 can be either +ve or -ve, giving 2 × 2 × 2 = 8 combinations of +ve and -ve.
Hence answer is 3 × 3 ! × 8 = 3 × 6 × 8 = 1 4 4 .