Math Problem Statement

Determine the values of x and y such that the matrix product A.B = C, and calculate 2x^2 - y.

Solution

The problem in the image involves matrix multiplication and solving for variables. Here's a breakdown of the task:

Given:

  • Matrix A=[2x322]A = \begin{bmatrix} 2x & 3 \\ -2 & 2 \end{bmatrix}
  • Matrix B=[452x]B = \begin{bmatrix} 4 & 5 \\ 2 & x \end{bmatrix}
  • Matrix C=[2y262y6]C = \begin{bmatrix} 2y & 26 \\ -2y & -6 \end{bmatrix}

We are asked to:

  1. Compute AB=CA \cdot B = C, and determine the values of xx and yy.
  2. Calculate 2x2y2x^2 - y.

Step 1: Matrix Multiplication AB=CA \cdot B = C

Multiplying matrices AA and BB:

AB=[2x322][452x]=[(2x4+32)(2x5+3x)(24+22)(25+2x)]A \cdot B = \begin{bmatrix} 2x & 3 \\ -2 & 2 \end{bmatrix} \cdot \begin{bmatrix} 4 & 5 \\ 2 & x \end{bmatrix} = \begin{bmatrix} (2x \cdot 4 + 3 \cdot 2) & (2x \cdot 5 + 3 \cdot x) \\ (-2 \cdot 4 + 2 \cdot 2) & (-2 \cdot 5 + 2 \cdot x) \end{bmatrix}

This simplifies to: AB=[8x+610x+3x8+410+2x]=[8x+613x42x10]A \cdot B = \begin{bmatrix} 8x + 6 & 10x + 3x \\ -8 + 4 & -10 + 2x \end{bmatrix} = \begin{bmatrix} 8x + 6 & 13x \\ -4 & 2x - 10 \end{bmatrix}

We now equate this result with matrix CC: [8x+613x42x10]=[2y262y6]\begin{bmatrix} 8x + 6 & 13x \\ -4 & 2x - 10 \end{bmatrix} = \begin{bmatrix} 2y & 26 \\ -2y & -6 \end{bmatrix}

Step 2: Set up equations from matrix equality

  • From the first element: 8x+6=2y8x + 6 = 2y
  • From the second element: 13x=2613x = 26
  • From the third element: 4=2y-4 = -2y
  • From the fourth element: 2x10=62x - 10 = -6

Step 3: Solve for xx and yy

From 13x=2613x = 26: x=2613=2x = \frac{26}{13} = 2

From 4=2y-4 = -2y: y=42=2y = \frac{-4}{-2} = 2

Substitute x=2x = 2 into 2x10=62x - 10 = -6: 2(2)10=6(True, so this is correct)2(2) - 10 = -6 \quad \text{(True, so this is correct)}

Now substitute x=2x = 2 into 8x+6=2y8x + 6 = 2y: 8(2)+6=2y16+6=2y22=2yy=118(2) + 6 = 2y \quad \Rightarrow \quad 16 + 6 = 2y \quad \Rightarrow \quad 22 = 2y \quad \Rightarrow \quad y = 11

Step 4: Compute 2x2y2x^2 - y

Substitute x=2x = 2 and y=11y = 11: 2x2y=2(2)211=2(4)11=811=32x^2 - y = 2(2)^2 - 11 = 2(4) - 11 = 8 - 11 = -3

Final Answer:

  • x=2x = 2
  • y=11y = 11
  • 2x2y=32x^2 - y = -3

Would you like a detailed explanation of any part of the process?

Here are 5 questions to explore this topic further:

  1. What are the steps involved in matrix multiplication?
  2. How can you verify that two matrices are equal?
  3. What are some common applications of matrix multiplication in real-world problems?
  4. How can systems of equations be solved using matrix operations?
  5. What are the properties of matrix operations (e.g., commutative, associative)?

Tip: When solving systems of equations from matrices, always check that the matrix dimensions are compatible for multiplication.

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Math Problem Analysis

Mathematical Concepts

Matrix Multiplication
Algebra
System of Equations

Formulas

Matrix multiplication formula: C[i,j] = A[i,1]*B[1,j] + A[i,2]*B[2,j]
System of linear equations

Theorems

Matrix multiplication and equality
Basic algebraic methods for solving systems of equations

Suitable Grade Level

Grades 10-12