There exists four integers a , b , c , d ≥ 0 such that: a 3 + b 3 + c 3 = d 2 Is the above statement true or false?
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Assuming we want non-zero integers, one example is ( a , b , c , d ) = ( 1 , 2 , 3 , 6 ) . There are many others
Is numerical example enough here? I can choose 0 3 + 1 3 + 2 3 = 3 2 . Also, this solution is not unique.
Zero isn’t a positive integer
I should edit the problem, sorry.
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The simplest (and most boring) solution is just ( 0 , 0 , 0 , 0 ) . A simple infinite family of solutions is ( 3 x 2 , 3 x 2 , 3 x 2 , 9 x 3 ) .
If we want the integers to be distinct, then ( 1 , 2 , 3 , 6 ) is the simplest solution. If ( a , b , c , d ) is a solution, then so is ( a x 2 , b x 2 , c x 2 , d x 3 ) , so there are infinitely many solutions with ( a , b , c , d ) distinct.
If we're feeling really picky, we might want to insist that g cd ( a , b , c , d ) = 1 . There seem to be lots of solutions satisfying this additional criterion, but I haven't yet found a rule to generate them - any suggestions?