Formula

Cramer's Rule for a System of Three Linear Equations

For a system of three linear equations represented as: {a1x+b1y+c1z=k1a2x+b2y+c2z=k2a3x+b3y+c3z=k3\left\{\begin{array}{l} a_1 x + b_1 y + c_1 z = k_1 \\\\ a_2 x + b_2 y + c_2 z = k_2 \\\\ a_3 x + b_3 y + c_3 z = k_3 \end{array}\right.

The solution (x,y,z)(x, y, z) can be determined using determinants: x=DxDx = \frac{D_x}{D}, y=DyDy = \frac{D_y}{D}, and z=DzDz = \frac{D_z}{D}

Where DD is the determinant of the coefficients of the variables: D=a1b1c1a2b2c2a3b3c3D = \begin{vmatrix} a_1 & b_1 & c_1 \\\\ a_2 & b_2 & c_2 \\\\ a_3 & b_3 & c_3 \end{vmatrix}

DxD_x is formed by replacing the xx-coefficients with the constants k1k_1, k2k_2, and k3k_3: Dx=k1b1c1k2b2c2k3b3c3D_x = \begin{vmatrix} k_1 & b_1 & c_1 \\\\ k_2 & b_2 & c_2 \\\\ k_3 & b_3 & c_3 \end{vmatrix}

DyD_y is formed by replacing the yy-coefficients with the constants: Dy=a1k1c1a2k2c2a3k3c3D_y = \begin{vmatrix} a_1 & k_1 & c_1 \\\\ a_2 & k_2 & c_2 \\\\ a_3 & k_3 & c_3 \end{vmatrix}

DzD_z is formed by replacing the zz-coefficients with the constants: Dz=a1b1k1a2b2k2a3b3k3D_z = \begin{vmatrix} a_1 & b_1 & k_1 \\\\ a_2 & b_2 & k_2 \\\\ a_3 & b_3 & k_3 \end{vmatrix}

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Updated 2026-04-29

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