Depending on the determinant of the coefficient matrix and consistency conditions, the system can have one, infinitely many, or no solutions.
If det(A) ≠ 0, then the system has a unique solution given by X = A⁻¹B.
If det(A) = 0, the system may be inconsistent (no solution) or dependent (infinitely many solutions).
All these methods can be applied to solve a system of 3 equations in 3 variables.
In Cramer’s Rule, x = det(A₁)/det(A), where A₁ is obtained by replacing the first column of A with constants column.
If det(A) = 0 and the equations are consistent, the system has infinitely many solutions (dependent).
The coefficient matrix is formed from the coefficients of x, y, z in each equation: [[2,1,-1],[1,-1,1],[3,2,1]].
X is the column matrix of unknowns [x, y, z]^T.
A system with no solution is called inconsistent.
A homogeneous system always has at least the trivial solution X = 0. Non-trivial solutions exist if det(A) = 0.