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Identify the given matrix and the values of its elements.

Mathematics

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Answer

D. -3\text{D. -3}

Step-by-step solution

4 steps
  1. Identify the given matrix and the values of its elements.

    The matrix AA is given as:

    A=(a11a12a21a22)A = \begin{pmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{pmatrix}

    The given values for the elements are:
    a11=1a_{11} = 1
    a22=1a_{22} = 1
    a21=2a_{21} = 2
    a12=2a_{12} = 2

  2. Substitute the given values into the matrix AA.

    A=(1221)A = \begin{pmatrix} 1 & 2 \\ 2 & 1 \end{pmatrix}
  3. Calculate the determinant of AA, denoted as ∣A∣|A|.

    For a 2×22 \times 2 matrix (abcd)\begin{pmatrix} a & b \\ c & d \end{pmatrix}, the determinant is calculated as ad−bcad - bc.
    Applying this formula to matrix AA:

    ∣A∣=(1)(1)−(2)(2)|A| = (1)(1) - (2)(2) ∣A∣=1−4|A| = 1 - 4 ∣A∣=−3|A| = -3
  4. Compare the result with the given options.

    The calculated determinant is −3-3. This matches option D.

    The final answer is D. -3\text{D. -3}.

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