If , what are the possible real values of ?

Answer and explanation

Correct answer: A.

  1. Step 1: Evaluate determinant: .
  2. Step 2: Set equal to 10: .
  3. Step 3: Take square root: .
Answer
\pm 4.
Why not the others: '' equates by subtracting 6; '' ignores the off-diagonal elements; '' forgets to take the square root.

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