Given a set of linear Diophantine Equations (LDE's), where each equation is one of the following for

Jeffery Clements

Jeffery Clements

Answered question

2022-06-16

Given a set of linear Diophantine Equations (LDE's), where each equation is one of the following form:
Let C be a positive integer constant. Also, the number of variables in each equation is exactly C.
1. a i + b i + c i . . . . . = C or
2. a i + b i + c i . . . . . = ( C + 1 )
For every such set of LDE problem instance, the problem is solvable iff, at least one such solution exists, such that each variable's assigned value in that solution is:
1. C
2. 0
In other words, the solution if it exists is bounded by the constant C and 0.
Can someone help with the proof of the above statement (or counterexamples with some small C)?

Answer & Explanation

sleuteleni7

sleuteleni7

Beginner2022-06-17Added 28 answers

So, if I understood properly your exposition, the system can be written as
{ x 1 + x 2 + + x c 1 = c 1 + d 1 x 1 + x 2 + + x c 2 = c 2 + d 2 x 1 + x 2 + + x c n = c n + d n
where d k { 0 , 1 }.
Clearly we can always rearrange the rows by increasing c k 's
{ x 1 + x 2 + + x c 1 = c 1 + d 1 x 1 + x 2 + + x c 1 + + x c 2 = c 2 + d 2 x 1 + x 2 + + x c 1 + + x c 2 + + + x c n 1 + + x c n = c n + d n
and subtracting from each row the preceding one
{ x 1 + x 2 + + x c 1 = c 1 + d 1 x c 1 + 1 + + x c 2 = ( c 2 c 1 ) + d 2 d 1 x c n 1 + 1 + + x c n = ( c n c n 1 ) + d n d n 1
This is not, actually, a set of equations but a collection of n independent equations, since the variables in each row are different from (i.e. not related to) those in the other rows.
Now, an equation of those, of the type
x 1 + x 2 + + x m = m + d ^ | d ^ = 1 , 0 , 1
can have solutions in which the various xk are not necessarily limited to the range [0,m].
Thus your claim is not justified.

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