Maths-
General
Easy
Question
If A is non-singular matrix of order 3 × 3, then adj (adj A) is equal to -
- |A| A
- |A|2 A
- |A|–1 A
- None of these
The correct answer is: |A| A
As A is a non-singular matrix A–1 = (adj A)
adj A = |A| A–1 = B(say).
Now,
adj (adj A) = adj (B) = |B|B–1 = ||A|A–1| (|A| A–1)–1
= |A|3 |A–1| |A|–1 (A–1)–1
= |A|3 · A
= |A| A.
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