Can ax + by + cz = d have an integer solution?

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In summary, the Diophantine equation ax + by + cz + d has an integer solution if and only if the gcd(a, b, c) divides d. This can be proven by starting with the simpler equation ax + d and adding the other terms one by one. The Linear Equation Theorem states that the equation ax + by = gcd(a, b) always has a solution in integers, which can be found using the Euclidean algorithm.
  • #1
ACardAttack
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Prove that the Diophantine equation ax+by+cz+d has an integer solution if and only if the gcd(a,b,c) divides d.

Got this on my homework for my proofs class. Help would be greatly appreciated.

Thanks
 
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  • #2
Start with a simpler equation, ax+d, and then try to add the other terms one by one.
 
  • #3
Dodo said:
Start with a simpler equation, ax+d, and then try to add the other terms one by one.

I goofed...it is actually ax+by+cz=d...does that make a difference?
 
  • #4
the Linear Equation Theorem says that the equation ax + by = gcd(a, b) always has a solution(s, u) in integers, and this solution can be found by the Euclidean algorithm, which we use to compute the gcd of a and b.
 
  • #5
I figured it out...thanks for the help
 
  • #6
ACardAttack said:
I goofed...it is actually ax+by+cz=d...does that make a difference?
Well, yes! It's an equation! ax+ by+ cz+ d isn't an equation.
 

FAQ: Can ax + by + cz = d have an integer solution?

How do you prove a Diophantine equation?

To prove a Diophantine equation, you need to show that there exists at least one solution that satisfies all the given conditions. This can be done through various methods such as substitution, elimination, or using modular arithmetic.

What is a Diophantine equation?

A Diophantine equation is an algebraic equation where the solutions are restricted to integers only. It is named after the ancient Greek mathematician Diophantus who studied these types of equations.

Can all Diophantine equations be solved?

No, not all Diophantine equations can be solved. Some equations have no solutions, while others may have infinitely many solutions. The difficulty of solving a Diophantine equation depends on the complexity of the equation and the techniques used to solve it.

What are some real-world applications of Diophantine equations?

Diophantine equations have various applications in fields such as cryptography, number theory, and computer science. They are used to solve problems related to finding integer solutions to equations, calculating the number of solutions, and determining patterns in the solutions.

Are there any famous unsolved Diophantine equations?

Yes, there are several famous unsolved Diophantine equations, including Fermat's Last Theorem, the Catalan's Conjecture, and the Goldbach's Conjecture. These equations have been studied for centuries and continue to intrigue mathematicians with their elusive solutions.

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