Question

if A is invertible matrix of order 3 and |A|= -7 then A-1 is

Answer 1

Answer:

the answer is :- ∵ A

−1

=

∣A∣

1

.adj A

Order of adj A is also 3×3

∣A

−1

∣=

∣

∣

∣

∣

∣A∣

1

adj A

∣

∣

∣

∣

=(

∣A∣

1

)

3

.∣adj A∣ [∵∣KA∣=K

n

.∣A∣, where n is order of A ]

=

∣A∣

3

1

.∣A∣

3−1

[∵∣Adj A∣=∣A∣

n−1

, where n is order of A]

∴∣A

−1

∣=

∣A∣

1

=

7

1

hope this will help u