Math Problem Statement

A matrix equation is given: X * [[2, -1], [5, -3]] = [[11, -6], [2, -2]]. Calculate the sum of the elements of matrix X.

Solution

The provided matrix equation is:

X(2153)=(11622)X \begin{pmatrix} 2 & -1 \\ 5 & -3 \end{pmatrix} = \begin{pmatrix} 11 & -6 \\ 2 & -2 \end{pmatrix}

You are asked to find matrix XX and calculate the sum of its elements.

Step 1: Solve for matrix XX

To solve for XX, multiply both sides of the equation by the inverse of matrix (2153)\begin{pmatrix} 2 & -1 \\ 5 & -3 \end{pmatrix}.

Let matrix A=(2153)A = \begin{pmatrix} 2 & -1 \\ 5 & -3 \end{pmatrix}. We need to find A1A^{-1}, the inverse of AA.

The inverse of a 2x2 matrix A=(abcd)A = \begin{pmatrix} a & b \\ c & d \end{pmatrix} is given by:

A1=1adbc(dbca)A^{-1} = \frac{1}{ad - bc} \begin{pmatrix} d & -b \\ -c & a \end{pmatrix}

For matrix A=(2153)A = \begin{pmatrix} 2 & -1 \\ 5 & -3 \end{pmatrix}:

  • a=2a = 2, b=1b = -1, c=5c = 5, and d=3d = -3
  • Determinant det(A)=adbc=(2)(3)(5)(1)=6+5=1\text{det}(A) = ad - bc = (2)(-3) - (5)(-1) = -6 + 5 = -1

Thus,

A1=11(3152)=(3152)A^{-1} = \frac{1}{-1} \begin{pmatrix} -3 & 1 \\ -5 & 2 \end{pmatrix} = \begin{pmatrix} 3 & -1 \\ 5 & -2 \end{pmatrix}

Step 2: Multiply both sides by A1A^{-1}

Now, multiply the right-hand side matrix (11622)\begin{pmatrix} 11 & -6 \\ 2 & -2 \end{pmatrix} by A1A^{-1} to find matrix XX:

X=(11622)(3152)X = \begin{pmatrix} 11 & -6 \\ 2 & -2 \end{pmatrix} \begin{pmatrix} 3 & -1 \\ 5 & -2 \end{pmatrix}

Let's calculate this multiplication step-by-step:

X=((113+(6)5)(111+(6)2)(23+(2)5)(21+(2)2))X = \begin{pmatrix} (11 \cdot 3 + (-6) \cdot 5) & (11 \cdot -1 + (-6) \cdot -2) \\ (2 \cdot 3 + (-2) \cdot 5) & (2 \cdot -1 + (-2) \cdot -2) \end{pmatrix}

Performing the calculations:

  • Top left element: 113+(6)5=3330=311 \cdot 3 + (-6) \cdot 5 = 33 - 30 = 3
  • Top right element: 111+(6)2=11+12=111 \cdot -1 + (-6) \cdot -2 = -11 + 12 = 1
  • Bottom left element: 23+(2)5=610=42 \cdot 3 + (-2) \cdot 5 = 6 - 10 = -4
  • Bottom right element: 21+(2)2=2+4=22 \cdot -1 + (-2) \cdot -2 = -2 + 4 = 2

Thus, matrix XX is:

X=(3142)X = \begin{pmatrix} 3 & 1 \\ -4 & 2 \end{pmatrix}

Step 3: Calculate the sum of the elements of XX

The sum of the elements in matrix XX is:

3+1+(4)+2=23 + 1 + (-4) + 2 = 2

Final Answer:

The sum of the elements of matrix XX is 22.


Do you want further details or have any questions about the solution?

Here are five related questions to expand your understanding:

  1. How do you find the inverse of a 3x3 matrix?
  2. What happens if the determinant of a matrix is zero?
  3. Can a non-square matrix have an inverse?
  4. How is matrix multiplication different from scalar multiplication?
  5. What are some applications of matrix equations in real-world problems?

Tip: Always verify the determinant before attempting to find the inverse of a matrix, as a zero determinant means the matrix is singular (non-invertible).

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Math Problem Analysis

Mathematical Concepts

Matrix Equations
Inverse Matrix
Matrix Multiplication

Formulas

Inverse of 2x2 matrix: A^(-1) = 1/(ad-bc) * [[d, -b], [-c, a]]
Matrix multiplication: C = A * B

Theorems

Matrix inverse theorem
Matrix multiplication theorem

Suitable Grade Level

Grades 10-12