Answer :

A ^{– 1} = B =

|B| = 1(3 – 0) – 2( – 1 – 0) – 2(2 – 0)

= 3 + 2 – 4

|B| = 1

Now, B ^{– 1} =

Cofactors of B are:

C_{11} = – 3 C_{21} = 2 C_{31} = 6

C_{12} = 1 C_{22} = 1 C_{32} = 2

C_{13} = 2 C_{23} = 2 C_{33} = 5

adj B =

=

So, adj B =

Now, B ^{– 1} =

(AB) ^{– 1 =} B ^{– 1} A ^{– 1}

=

Hence, =

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PREVIOUSFind the adjoint of the matrix and hence show that A(adj A) = |A| I3.NEXTA shopkeeper has 3 varities of pens ‘A’, ‘B’ and ‘C’. Meenu purchased 1 pen of each variety for a total of ₹21. Jeen purchased 4 pens of ‘A’ variety, 3 pens of ‘B’ variety and 2 pens of ‘C’ variety for ₹60. While Shikha purchased 6 pens of ‘A’ variety, 2 pens of ‘B’ variety and 3 pens of ‘C’ variety for ₹70. Using matrix method find the cost of each pen.

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