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Given A = [240396] and B = [142813] is (AB)′ = B′A′?

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Question

Given A = `[(2, 4, 0),(3, 9, 6)]` and B = `[(1, 4),(2, 8),(1, 3)]` is (AB)′ = B′A′? 

Sum
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Solution

Here, A  = `[(2, 4, 0),(3, 9, 6)]`, B = `[(1, 4),(2, 8),(1, 3)]`

AB = `[(2, 4, 0),(3, 9, 6)] [(1, 4),(2, 8),(1, 3)]`

= `[(2 + 8 + 0, 8 + 32 + 0),(3 + 18 + 6, 12 + 72 + 18)]`

= `[(10, 40),(27, 102)]`

L.H.S. (AB)' = `[(10, 27),(40, 102)]`

Now B = `[(1, 4),(2, 8),(1, 3)]`

⇒ B' = `[(1, 2, 1),(4, 8, 3)]`

A = `[(2, 4, 0),(3, 9, 6)]`

⇒ A' = `[(2, 3),(4, 90),(0, 6)]`

R.H.S. B'A' = `[(1, 2, 1),(4, 8, 3)][(2, 3),(4, 9),(0, 6)]`

= `[(2 + 8 + 0, 3 + 18 + 6),(8 + 32 + 0, 12  72 + 18)]`

=`[(10, 27),(40, 102)]`

= L.H.S.

Hence, L.H.S. = R.H.S.

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Chapter 3: Matrices - Exercise [Page 54]

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NCERT Exemplar Mathematics Exemplar [English] Class 12
Chapter 3 Matrices
Exercise | Q 17 | Page 54

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