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Find all solutions in integers of \(x^3+2 y^3=4 z^3\).

Short Answer

Expert verified
(0, 0, 0) is the only integer solution.

Step by step solution

01

Analyze the Diophantine Equation

Consider the equation given: \[x^3 + 2y^3 = 4z^3\]We are tasked with finding all integer solutions \(x, y, z\) that satisfy this equation.
02

Check for Trivial Solutions

Firstly, consider the simplest solution, where \(x, y, z\) are zero: \[(0)^3 + 2(0)^3 = 4(0)^3 \Rightarrow 0 = 0\]Thus, \(x = 0, y = 0, z = 0\) is a trivial solution.
03

Substitute Small Integer Values

Next, substitute small integer values to check for other possible solutions. We test a few combinations:For \(z = 1:\) \[x^3 + 2y^3 = 4(1)^3 \Rightarrow x^3 + 2y^3 = 4\]Trying some values: For \(x = 0\):\[0 + 2y^3 = 4 \Rightarrow y^3 = 2\] There are no real integer values for \(y\) such that \(y^3 = 2\).Similarly, test other small values and find there are no other integer solutions.
04

Consider Symmetry and Factorization

Rewrite the equation in terms of factoring or symmetry. As the entire equation is symmetrical, observe that other than \(x, y, z = 0\), we do not obtain any other integer solutions using elementary algebraic techniques and basic checks.
05

Verify Solutions

So, verify the solution:For \(x = 0, y = 0, z = 0:\)\[0^3 + 2(0)^3 = 4(0)^3 \Rightarrow 0 = 0\]Thus, \( (0, 0, 0)\) is a valid integer solution.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Integer Solutions
Diophantine equations seek integer solutions to polynomial equations. In this context, an integer solution means that the variables must be whole numbers (which can be positive, negative, or zero). For our equation, \(x^3 + 2y^3 = 4z^3\), we are looking for values of \(x, y,\) and \(z\) that satisfy the equation and are integers. This concept is fundamental because many equations have solutions in real numbers but not in integers. Understanding integer solutions involves checking possible numbers systematically, starting from simple cases like zero or small values to see if they fit the equation. For example, checking \(x = 0, y = 0,\) and \(z = 0\), we find that this trivial solution satisfies the equation:
\[(0)^3 + 2(0)^3 = 4(0)^3 \Rightarrow 0 = 0\]
Thus, (0, 0, 0) is an obvious integer solution.
Diophantine Analysis
Diophantine analysis involves methods and strategies to solve equations like \(x^3 + 2y^3 = 4z^3\) with integer solutions. The first step is often to check for trivial solutions where variables are zero. Beyond trivial solutions, we try substituting small integer values to find if there are any other solutions.

For instance, setting \(z = 1\), we get the equation:
\[x^3 + 2y^3 = 4(1)^3 \Rightarrow x^3 + 2y^3 = 4\]
Testing small values like \(x = 0\), we get
\[0 + 2y^3 = 4\Rightarrow y^3 = 2\]
Since \(y = \sqrt[3]{2}\) is not an integer, there are no integer solutions for this set of values. Diophantine analysis often requires checking multiple values systematically. Observing that no small values work reinforces the need to employ algebraic strategies or more complex methods.
Factoring and Symmetry
Factoring and symmetry can simplify solving Diophantine equations. Factoring involves rewriting terms to reveal patterns or solutions. Symmetry allows seeing relationships between variables that might not be obvious. For example, the symmetry in the equation \(x^3 + 2y^3 = 4z^3\) can be looked at by reframing the terms but maintains the form regardless of the signs of \(x\), \(y\), or \(z\).

Factoring can sometimes break down complex terms into simpler parts, though for this specific problem, simple factoring tools reveal that:
\[x^3 + 2y^3 = 4z^3\]
does not yield integer solutions beyond the trivial \(x = 0, y = 0, z = 0\). Recognizing symmetry helps ensure all potential integer combinations have been considered. Despite these strategies, this equation only has the trivial integer solution.

Overall, understanding the power of factoring and symmetry is essential for tackling more challenging problems in Diophantine analysis.

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