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If A=[1−111−2−2213]A = \begin{bmatrix} 1 & -1 & 1 \\ 1 & -2 & -2 \\ 2 & 1 & 3 \end{bmatrix} and square matrix BB satisfy AB=8IAB = 8I, then the value of ∣B∣|B| is:

Solution

✅ Correct Option: 2

Compute ∣A∣|A|: expanding along row 1: 1(−6+2)−(−1)(3+4)+1(1+4)=−4+7+5=81(-6+2) - (-1)(3+4) + 1(1+4) = -4 + 7 + 5 = 8. From AB=8IAB = 8I: ∣AB∣=∣8I∣=83=512|AB| = |8I| = 8^3 = 512. Also ∣AB∣=∣A∣∣B∣|AB| = |A||B|, so ∣B∣=512/∣A∣=512/8=64|B| = 512/|A| = 512/8 = 64.

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