Practicing Success
Statement-1: If A and B are two non-singular matrices of the same order, then $adj (AB) = (adj\, B) (adj\, A)$ Statement-2: $A (adj\, A) = |A|I$ |
Statement-1 is True, Statement-2 is true; Statement-2 is a correct explanation for Statement-1. Statement-1 is True, Statement-2 is True; Statement-2 is not a correct explanation for Statement-1. Statement-1 is True, Statement-2 is False. Statement-1 is False, Statement-2 is True. |
Statement-1 is True, Statement-2 is true; Statement-2 is a correct explanation for Statement-1. |
We have, $(AB) (adj\, AB) =|AB| I$ ...(i) $[∵A (adj\, A) =|A|I]$ $(AB) (adj\, B adj\, A) = A (B\, adj\, B) adj\, A$ $⇒(AB) (adj\, B\, adj\, A)=(A(|B|I)) adj\,A$ $[∵ B (adj\, B) =|B| I]$ $⇒(AB) (adj\, B\, adj\, A) =|B| (A\, adj\, A)$ $⇒(AB) (adj\, B\, adj\, A) =|B||A| I=|AB| I$ ...(ii) From (i) and (ii), we get $∴adj\, (AB) = (adj\, B) (adj\, A)$ |