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Does Infinite Solutions Mean Inconsistent?

Published in Linear Algebra 2 mins read

No, infinite solutions mean a system of equations is consistent and dependent, not inconsistent.

Here's a breakdown:

  • Consistent System: A system of equations is considered consistent if it has at least one solution (either one solution or an infinite number of solutions).

  • Inconsistent System: A system of equations is considered inconsistent if it has no solution.

  • Dependent System: A consistent system with an infinite number of solutions is considered dependent. This typically means the equations represent the same line or plane (in higher dimensions). One equation is essentially a multiple of the other.

  • Independent System: A consistent system with exactly one solution is considered independent.

Here's a table summarizing the relationships:

System Type Number of Solutions Description
Consistent One solution Independent. The equations intersect at a single point.
Consistent Infinite solutions Dependent. The equations represent the same line (or plane in higher dimensions). Every solution of one equation is also a solution of the other.
Inconsistent No solution The equations represent parallel lines (or planes that never intersect). There is no solution that satisfies all equations simultaneously.

Example:

Consider the following system of equations:

  1. x + y = 2
  2. 2x + 2y = 4

Notice that the second equation is simply the first equation multiplied by 2. Therefore, they represent the same line. Any solution to the first equation will also be a solution to the second equation. This system has infinite solutions (e.g., (0, 2), (1, 1), (2, 0), etc.). This is a consistent and dependent system.

On the other hand, the system:

  1. x + y = 2
  2. x + y = 3

has no solution because there are no values of x and y that can simultaneously satisfy both equations. This is an inconsistent system.

In conclusion, if a system of equations has infinite solutions, it is classified as consistent (specifically, consistent and dependent), not inconsistent. Inconsistent systems have no solutions.

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