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Determinants, Adjoint & Inverse · Question 64 of 87

Question 64

HardOriginal question

AA and BB are square matrices of order 3 with ∣A∣=2|A| = 2 and ∣B∣=−3|B| = -3. What is ∣2AB∣|2AB|?

Options for question 64

Show the answer and explanation
CorrectNot quiteAnswer A

Correct answer: A

Explanation

  1. ∣AB∣=∣A∣∣B∣=−6|AB| = |A||B| = -6.

  2. 2AB2AB is a 3 × 3 matrix times 2, so ∣2AB∣=23∣AB∣=8(−6)=−48|2AB| = 2^3|AB| = 8(-6) = -48.

Worth noting

−12-12 takes the 2 out once; it comes out once for each of the three rows.

Concept
Determinant of a product
Typical time
120 s
Your time
—
The rule this testsThe adjoint and the inverse
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Ten questions from Determinants, Adjoint & Inverse, at your own pace.

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Ten questions from Determinants, Adjoint & Inverse, at your own pace.