An indeterminate equation, in mathematics, is an equation for which there is more than one solution; for example, 2x = y is a simple indeterminate equation, as are ax + by = c and x2 = 1. Indeterminate equations cannot be solved uniquely. Prominent examples include the following:
Univariate polynomial equation:
which has multiple solutions for the variable x in the complex plane unless it can be rewritten in the form
Non-degenerate conic equation:
where at least one of the given parameters A, B, and C is non-zero, and x and y are real variables.
Pell's equation:
where P is a given integer that is not a square number, and in which the variables x and y are required to be integers.
The equation of Pythagorean triples:
in which the variables x, y, and z are required to be positive integers.
The equation of the Fermat–Catalan conjecture:
in which the variables a, b, c are required to be coprime positive integers and the variables m, n, and k are required to be positive integers the sum of whose reciprocals is less than 1.