Math Problem Statement

Multiply the matrices \( A = \begin{bmatrix} -1 & -2 & 1 & -2 \\ 3 & 2 & 3 & 0 \\ -2 & 1 & 1 & -2 \end{bmatrix} \) and \( B = \begin{bmatrix} 1 & 2 & -2 \\ 1 & -2 & 3 \\ 2 & -2 & -2 \\ 1 & 0 & 0 \end{bmatrix} \).

Solution

To multiply the matrices AA and BB, we need to perform matrix multiplication, which involves taking the dot product of rows from AA with columns from BB.

Given matrices:

Matrix AA: A=[121232302112]A = \begin{bmatrix} -1 & -2 & 1 & -2 \\ 3 & 2 & 3 & 0 \\ -2 & 1 & 1 & -2 \end{bmatrix}

Matrix BB: B=[122123222100]B = \begin{bmatrix} 1 & 2 & -2 \\ 1 & -2 & 3 \\ 2 & -2 & -2 \\ 1 & 0 & 0 \end{bmatrix}

Dimensions:

  • Matrix AA is 3×43 \times 4.
  • Matrix BB is 4×34 \times 3.

The resulting matrix C=A×BC = A \times B will have dimensions 3×33 \times 3 (since AA has 3 rows and BB has 3 columns).

Step-by-Step Calculation:

Let’s calculate each element in CC by taking the dot product of each row of AA with each column of BB.

  1. Element C11C_{11}: C11=(1×1)+(2×1)+(1×2)+(2×1)=12+22=3C_{11} = (-1 \times 1) + (-2 \times 1) + (1 \times 2) + (-2 \times 1) = -1 - 2 + 2 - 2 = -3

  2. Element C12C_{12}: C12=(1×2)+(2×2)+(1×2)+(2×0)=2+42+0=0C_{12} = (-1 \times 2) + (-2 \times -2) + (1 \times -2) + (-2 \times 0) = -2 + 4 - 2 + 0 = 0

  3. Element C13C_{13}: C13=(1×2)+(2×3)+(1×2)+(2×0)=262+0=6C_{13} = (-1 \times -2) + (-2 \times 3) + (1 \times -2) + (-2 \times 0) = 2 - 6 - 2 + 0 = -6

  4. Element C21C_{21}: C21=(3×1)+(2×1)+(3×2)+(0×1)=3+2+6+0=11C_{21} = (3 \times 1) + (2 \times 1) + (3 \times 2) + (0 \times 1) = 3 + 2 + 6 + 0 = 11

  5. Element C22C_{22}: C22=(3×2)+(2×2)+(3×2)+(0×0)=646+0=4C_{22} = (3 \times 2) + (2 \times -2) + (3 \times -2) + (0 \times 0) = 6 - 4 - 6 + 0 = -4

  6. Element C23C_{23}: C23=(3×2)+(2×3)+(3×2)+(0×0)=6+66+0=6C_{23} = (3 \times -2) + (2 \times 3) + (3 \times -2) + (0 \times 0) = -6 + 6 - 6 + 0 = -6

  7. Element C31C_{31}: C31=(2×1)+(1×1)+(1×2)+(2×1)=2+1+22=1C_{31} = (-2 \times 1) + (1 \times 1) + (1 \times 2) + (-2 \times 1) = -2 + 1 + 2 - 2 = -1

  8. Element C32C_{32}: C32=(2×2)+(1×2)+(1×2)+(2×0)=422+0=8C_{32} = (-2 \times 2) + (1 \times -2) + (1 \times -2) + (-2 \times 0) = -4 - 2 - 2 + 0 = -8

  9. Element C33C_{33}: C33=(2×2)+(1×3)+(1×2)+(2×0)=4+32+0=5C_{33} = (-2 \times -2) + (1 \times 3) + (1 \times -2) + (-2 \times 0) = 4 + 3 - 2 + 0 = 5

Resulting Matrix CC:

C=[3061146185]C = \begin{bmatrix} -3 & 0 & -6 \\ 11 & -4 & -6 \\ -1 & -8 & 5 \end{bmatrix}

Would you like further explanation or details on matrix multiplication?


Here are some questions for further exploration:

  1. How do you perform matrix multiplication with matrices of different sizes?
  2. Why is matrix multiplication not commutative?
  3. How can the properties of matrices simplify complex calculations?
  4. What are some practical applications of matrix multiplication in data science?
  5. How do special matrices (like identity or zero matrices) interact with other matrices?

Tip: Always check the dimensions of matrices before multiplying to ensure they are compatible for the operation.

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Math Problem Analysis

Mathematical Concepts

Matrix Multiplication
Linear Algebra

Formulas

Dot product for matrix multiplication: C_ij = sum(A_i * B_j)

Theorems

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Suitable Grade Level

Grades 10-12