Math Problem Statement

Diketahui matriks A = [3 2; 0 5] dan B = [-3 -1; -17 0]. Jika AX = B + A^T, tentukan determinan matriks X!

Solution

The problem provided asks to find the determinant of matrix XX, given the matrices AA and BB, and the equation AX=B+ATAX = B + A^T, where ATA^T is the transpose of matrix AA.

Let's break it down:

Given Matrices:

A=[3205],B=[31170]A = \begin{bmatrix} 3 & 2 \\ 0 & 5 \end{bmatrix}, \quad B = \begin{bmatrix} -3 & -1 \\ -17 & 0 \end{bmatrix} The equation is: AX=B+ATAX = B + A^T where ATA^T is the transpose of AA, so: AT=[3025]A^T = \begin{bmatrix} 3 & 0 \\ 2 & 5 \end{bmatrix} Now, the equation becomes: AX=B+AT=[31170]+[3025]AX = B + A^T = \begin{bmatrix} -3 & -1 \\ -17 & 0 \end{bmatrix} + \begin{bmatrix} 3 & 0 \\ 2 & 5 \end{bmatrix} B+AT=[3+31+017+20+5]=[01155]B + A^T = \begin{bmatrix} -3 + 3 & -1 + 0 \\ -17 + 2 & 0 + 5 \end{bmatrix} = \begin{bmatrix} 0 & -1 \\ -15 & 5 \end{bmatrix} So the equation simplifies to: AX=[01155]AX = \begin{bmatrix} 0 & -1 \\ -15 & 5 \end{bmatrix} To find XX, we need to multiply both sides of the equation by the inverse of matrix AA: X=A1[01155]X = A^{-1} \begin{bmatrix} 0 & -1 \\ -15 & 5 \end{bmatrix}

Step 1: Find A1A^{-1}

The inverse of a 2x2 matrix A=[abcd]A = \begin{bmatrix} a & b \\ c & d \end{bmatrix} is given by: A1=1det(A)[dbca]A^{-1} = \frac{1}{\text{det}(A)} \begin{bmatrix} d & -b \\ -c & a \end{bmatrix} First, calculate the determinant of AA: det(A)=(3)(5)(0)(2)=15\text{det}(A) = (3)(5) - (0)(2) = 15 Now, the inverse of AA is: A1=115[5203]=[5152150315]=[13215015]A^{-1} = \frac{1}{15} \begin{bmatrix} 5 & -2 \\ 0 & 3 \end{bmatrix} = \begin{bmatrix} \frac{5}{15} & \frac{-2}{15} \\ 0 & \frac{3}{15} \end{bmatrix} = \begin{bmatrix} \frac{1}{3} & \frac{-2}{15} \\ 0 & \frac{1}{5} \end{bmatrix}

Step 2: Multiply A1A^{-1} with [01155]\begin{bmatrix} 0 & -1 \\ -15 & 5 \end{bmatrix}

X=[13215015][01155]X = \begin{bmatrix} \frac{1}{3} & \frac{-2}{15} \\ 0 & \frac{1}{5} \end{bmatrix} \begin{bmatrix} 0 & -1 \\ -15 & 5 \end{bmatrix} Now perform the matrix multiplication: X11=(13×0)+(215×15)=0+2=2X_{11} = \left(\frac{1}{3} \times 0\right) + \left(\frac{-2}{15} \times -15\right) = 0 + 2 = 2 X12=(13×1)+(215×5)=13+(1015)=1323=1X_{12} = \left(\frac{1}{3} \times -1\right) + \left(\frac{-2}{15} \times 5\right) = -\frac{1}{3} + \left(\frac{-10}{15}\right) = -\frac{1}{3} - \frac{2}{3} = -1 X21=(0×0)+(15×15)=03=3X_{21} = \left(0 \times 0\right) + \left(\frac{1}{5} \times -15\right) = 0 - 3 = -3 X22=(0×1)+(15×5)=0+1=1X_{22} = \left(0 \times -1\right) + \left(\frac{1}{5} \times 5\right) = 0 + 1 = 1 Thus, matrix XX is: X=[2131]X = \begin{bmatrix} 2 & -1 \\ -3 & 1 \end{bmatrix}

Step 3: Find the determinant of XX

The determinant of matrix XX is 1-1.

Would you like more details or have any further questions? Here are some related problems for practice:

  1. Calculate the determinant of a matrix using different methods.
  2. Solve a similar problem but with different matrices AA and BB.
  3. How do you find the inverse of a 3x3 matrix?
  4. Can a matrix with a determinant of zero have an inverse?
  5. What are the properties of determinants in matrix multiplication?

Tip: When multiplying matrices, make sure to check the dimensions of the matrices to ensure they can be multiplied. The number of columns in the first matrix must equal the number of rows in the second matrix.

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Math Problem Analysis

Mathematical Concepts

Matrix Algebra
Matrix Transpose
Matrix Inversion
Determinants

Formulas

Matrix multiplication: AX = B + A^T
Inverse of a 2x2 matrix: A^(-1) = 1/det(A) * [d -b; -c a]
Determinant of a 2x2 matrix: det(A) = ad - bc

Theorems

Properties of Determinants
Inverse Matrix Theorem

Suitable Grade Level

Grades 10-12