Given:
- A and B are square matrices of order 3
- ∣A∣=−1
- ∣B∣=5
For an n×n matrix M and scalar k:
∣kM∣=kn×∣M∣
For matrices A and B:
∣AB∣=∣A∣×∣B∣
Since the matrices are of order 3:
∣3AB∣=33×∣AB∣
∣3AB∣=27×∣AB∣
Finding ∣AB∣:
∣AB∣=∣A∣×∣B∣
∣AB∣=(−1)×5
∣AB∣=−5
∣3AB∣=27×∣AB∣
∣3AB∣=27×(−5)
∣3AB∣=−135
Therefore, the value of ∣3AB∣=−135