If A = , find . Using solve the system of equations 2x - 3y + 5z = 11 3x + 2y - 4z = -5 x + y - 2z = -3
The system of equations can be written in matrix form as AX = B, where A = , X = , B =
Step 1: Find |A| |A| = 2[(2)(-2) - (-4)(1)] - (-3)[(3)(-2) - (-4)(1)] + 5[(3)(1) - (2)(1)] = 2(0) + 3(-2) + 5(1) = -1 0 Since |A| 0, exists.
Step 2: Find cofactors A_{11} = 0, A_{12} = 2, A_{13} = 1 A_{21} = -1, A_{22} = -9, A_{23} = -5 A_{31} = 2, A_{32} = 23, A_{33} = 13
Step 3: Find adj(A) and adj(A) = = (1/|A|) × adj(A) =
Step 4: Solve for X X = B = =
Hence, x = 1, y = 2, z = 3.
Explanation
This question follows the standard matrix method for solving a system of linear equations, as demonstrated in Example 17 of the textbook. First, we verify that the coefficient matrix A is nonsingular by checking |A| 0. Then we find the inverse using the formula = (1/|A|) × adj(A), where adj(A) is the transpose of the cofactor matrix. Finally, we use X = B to find the solution.
Solution Steps
Step 1: Calculate determinant |A| = -1 0, confirming exists
Step 2: Calculate all 9 cofactors of matrix A
Step 3: Form adj(A) by transposing cofactor matrix, then find
Step 4: Multiply with B to get X = [1, 2, 3]^T