# Diophantine Equations

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## diophantine equations

[¦dī·ə¦fant·ən i′kwā·zhənz]
(mathematics)
Equations with more than one independent variable and with integer coefficients for which integer solutions are desired.

## Diophantine Equations

(named after the ancient Greek mathematician Diophantus), algebraic equations or systems of algebraic equations with integral coefficients, where the number of unknowns exceeds the number of equations and where we are looking for integral or rational solutions. The concept of Diophantine equations has been broadened in modern mathematics: they are equations in which the required solutions are algebraic numbers. Diophantine equations are also called indeterminate equations.

The simplest Diophantine equation is ax + by = 1, where a and b are relatively prime integers. This equation has an infinite number of solutions: if x0 and y0 are one solution, then the numbers x = x0, + bn and y = y0an (n is any integer) will also be solutions. Thus, all integral solutions of the equation 2x + 3y = 1 are obtained from the formulas x = 2 + 3n and y = −1 − 2n (here, x0 = 2 and y0 = −1). Another example of a Diophantine equation is x2 + y2 = z2. The positive integral solutions of this equation are the lengths of the legs x and y and the hypotenuse z of right triangles whose sides are integral and are called Pythagorean numbers. All triplets of relatively prime Pythagorean numbers can be obtained from the formulas x = m2n2, y = 2mn, and z = m2 + n2, where m and n are integers (m > n > 0).

In his work Arithmetica, Diophantus attempted to find rational (not necessarily integral) solutions for special types of Diophantine equations. The general theory of Diophantine equations of the first degree was developed in the 17th century by the French mathematician C.-G. Bachet de Meziriac. By the early 19th century P. de Fermat, J. Wallis, L. Euler, J. Lagrange, and K. Gauss had investigated Diophantine equations of the type

ax2 + bxy + cy2 + dx + ey + f = 0

where a, b, c, d, e, and f are integers, that is, a general nonhomogeneous equation of the second degree in two unknowns. Fermat maintained, for example, that the Diophantine equation x2dy2 = 1 (the Pellian equation), where d is a positive integer that is not a perfect square, has an infinite number of solutions. Wallis and Euler provided methods for solving this equation, and Lagrange proved that the number of solutions was infinite. Using continued fractions, Lagrange studied the general nonhomogeneous Diophantine equation of the second degree in two unknowns. Gauss constructed a general theory of quadratic forms that serves as the basis for solving certain types of Diophantine equations. Only in the 20th century were important gains made in the study of Diophantine equations in two unknowns of degree higher than the second. A. Thue showed that the Diophantine equation

a0xn + a1xn−1y + … + anyn = c

(where n ≥ 3; and a0, a1, …, an and c are integers and the polynomial a0tn + a1tn−1 + … + an is irreducible in the field of rational numbers) cannot have an infinite number of integral solutions. The British mathematician A. Baker obtained bounds on the solutions of some of these equations. The method of B. N. Delone applies to a narrower class of Diophantine equations but yields bounds on the number of solutions. In particular, his method completely solves Diophantine equations of the form

ax3 + y3 = 1

There are many directions in the theory of Diophantine equations. Thus, Fermat’s last theorem is a well-known problem in the theory of Diophantine equations. Soviet mathematicians (B. N. Delone, A. O. Gel’fond, and D. K. Faddeev, among others) have made fundamental contributions to the theory of Diophantine equations.

### REFERENCES

Gel’fond, A. O. Reshenie uravnenii v tselykh chislakh, 2nd ed. Moscow, 1956.
Dickson, L. E. History of the Theory of Numbers, vol. 2. Washington, D.C., 1920.
Skolem, Th. Diophantische Gleichungen. Berlin, 1938.
References in periodicals archive ?
Jones, Trigonometric Diophantine equations (On vanishing sums of roots of unity), Acta Arith.
Test Diophantine equations Equation Solutions in the range el 4x + 9y = 91 11 e2 10x + 7y = 97 10 e3 24x + 15y = 9 13 e4 19x + 23y = 3 4 e5 [x.
Unlike most other Diophantine equations, LDEs can be solved algorithmically (Rowe, 1986; Stewart, 1992).
While oversight and carelessness could still account for the above lapses, the situation becomes more serious when one turns to the editor's own account of the history of Diophantine equations and finds that there is no reference to Sesiano's English translation of the Arabic text of the lost Greek books of Diophantus' Arithmetica.
Penrose draws upon classes of mathematical problems for which no computational solution exists, including the tiling problem as well as certain Diophantine equations.
While solving these equations is difficult in general, we show that is also unnecessary, as mathematical techniques for manipulating Diophantine equations allow us to relatively easily compute and/or reduce the number of possible solutions, where each solution corresponds to a potential cache miss.
As an application of theorem 2, one may consider the integer solutions of decomposable diophantine equations of several variables.
Among the topics are the theory and application of plane partitions, linear homogeneous Diophantine equations and magic labelings of graphs, two combinatorial applications of the Aleksandrov-Fenchel inequalities, on the number of reduced decompositions of elements of Coxeter groups, and a symmetric function generalization of the chromatic polynomial of a graph.
1) leads to a system of certain quadratic Diophantine equations, for which a parametric solution is found.
The applied control synthesis method is based on the polynomial approach [1, 2] and solution of Diophantine equations [6].
Cohen, Number theory volume I: Tools and Diophantine equations, Springer Science + Bussiness Media, New York, 2007.

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