If the system of inequalities in
has no solution, and the linear equation in , , has a non-negative integer solution, find the sum of all integers that satisfy both conditions.
Rewrite the second inequality with x isolated. From we get . Dividing by the negative number reverses the direction: .
Translate no solution into a condition on m. The system asks for and at the same time. Such an fails to exist exactly when the upper bound does not sit strictly above the lower bound, i.e. . That gives , so .
Solve the linear equation. gives , so .
Impose non-negative integer on that root. Non-negativity needs , i.e. . Integrality needs to be even, so must be even.
Intersect the three conditions. Combining , and even over the integers leaves .
Check each survivor. : system needs and (empty), root . : and (empty), root . : and (empty), root . All three qualify, and .
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