Example

Example: Solving a System of Three Equations Using Cramer's Rule

Solve the system of equations using Cramer's rule: \left\{\begin{array}{l} 3x - 5y + 4z = 5 \\ 5x + 2y + z = 0 \\ 2x + 3y - 2z = 3 \end{array} ight.. First, evaluate the main determinant DD using the coefficients of the variables. By expanding by minors, we find D=37D = -37. Next, evaluate DxD_x by using the constants to replace the coefficients of xx; expanding by minors yields Dx=74D_x = -74. Then, evaluate DyD_y by replacing the coefficients of yy with the constants, yielding Dy=111D_y = 111. Finally, evaluate DzD_z by replacing the coefficients of zz with the constants, which yields Dz=148D_z = 148. Find the values of xx, yy, and zz by substituting into the formulas: x=DxD=7437=2x = \frac{D_x}{D} = \frac{-74}{-37} = 2, y=DyD=11137=3y = \frac{D_y}{D} = \frac{111}{-37} = -3, and z=DzD=14837=4z = \frac{D_z}{D} = \frac{148}{-37} = -4. Write the solution as the ordered triple (2,3,4)(2, -3, -4) and check that it is a solution to all three original equations.

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Updated 2026-04-28

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