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If A and B are square matrices of order 3 such that |A| = -1 and |B| = 5, then the value of |3AB| is

Solution

Correct Option: 4

Given:

  • A and B are square matrices of order 3
  • A=1|A| = -1
  • B=5|B| = 5

For an n×nn \times n matrix M and scalar k:

kM=kn×M|kM| = k^n \times |M|

For matrices A and B:

AB=A×B|AB| = |A| \times |B|


Since the matrices are of order 3:

3AB=33×AB|3AB| = 3^3 \times |AB|

3AB=27×AB|3AB| = 27 \times |AB|


Finding AB|AB|:

AB=A×B|AB| = |A| \times |B|

AB=(1)×5|AB| = (-1) \times 5

AB=5|AB| = -5


3AB=27×AB|3AB| = 27 \times |AB|

3AB=27×(5)|3AB| = 27 \times (-5)

3AB=135|3AB| = -135

Therefore, the value of 3AB=135|3AB| = -135

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