Evaluate the determinant \( \begin{vmatrix} 1 & 2 & 1 \\ 2 & 3 &

Practice Questions

Q1
Evaluate the determinant \( \begin{vmatrix} 1 & 2 & 1 \\ 2 & 3 & 1 \\ 3 & 4 & 1 \end{vmatrix} \)
  1. 0
  2. 1
  3. 2
  4. 3

Questions & Step-by-Step Solutions

Evaluate the determinant \( \begin{vmatrix} 1 & 2 & 1 \\ 2 & 3 & 1 \\ 3 & 4 & 1 \end{vmatrix} \)
Correct Answer: 0
  • Step 1: Write down the matrix for which we want to find the determinant: \( A = \begin{pmatrix} 1 & 2 & 1 \\ 2 & 3 & 1 \\ 3 & 4 & 1 \end{pmatrix} \).
  • Step 2: Identify the rows of the matrix: Row 1 is (1, 2, 1), Row 2 is (2, 3, 1), and Row 3 is (3, 4, 1).
  • Step 3: Check if the rows are linearly dependent. This means we need to see if one row can be formed by a combination of the others.
  • Step 4: Notice that Row 2 can be obtained by adding Row 1 and Row 1 (1 + 1 = 2, 2 + 1 = 3, 1 + 0 = 1).
  • Step 5: Since Row 2 can be formed from Row 1, the rows are linearly dependent.
  • Step 6: When the rows of a matrix are linearly dependent, the determinant is 0.
  • Step 7: Therefore, the determinant of the matrix is 0.
  • Determinants – The determinant of a matrix is a scalar value that can be computed from its elements and provides important properties about the matrix, such as whether it is invertible.
  • Linear Dependence – Rows (or columns) of a matrix are linearly dependent if at least one row (or column) can be expressed as a linear combination of others, which results in a determinant of zero.
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