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If A and B are square matrices of order 3 such that ∣A∣=3|A| = 3 and ∣B∣=−1|B| = -1, then ∣3AB∣|3AB| is equal to

Solution

✅ Correct Option: 2

Given that A and B are square matrices of order 3 with ∣A∣=3|A| = 3 and ∣B∣=−1|B| = -1.

When multiplying a matrix by a scalar kk, the determinant becomes:

∣kM∣=kn×∣M∣|kM| = k^n \times |M|

where nn is the order of the matrix.

For a matrix of order 3:

∣3AB∣=33×∣AB∣|3AB| = 3^3 \times |AB|

∣3AB∣=27×∣AB∣|3AB| = 27 \times |AB|


The determinant of a product of matrices is:

∣AB∣=∣A∣×∣B∣|AB| = |A| \times |B|

Substituting the given values:

∣AB∣=3×(−1)|AB| = 3 \times (-1)

∣AB∣=−3|AB| = -3


Combining the results:

∣3AB∣=27×∣AB∣|3AB| = 27 \times |AB|

∣3AB∣=27×(−3)|3AB| = 27 \times (-3)

∣3AB∣=−81|3AB| = -81

Therefore, ∣3AB∣=−81|3AB| = -81.

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