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The value of Cofactor of element a21 in matrix A = [125-8] is ______ - Mathematics and Statistics

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प्रश्न

The value of Cofactor of element a21 in matrix A = `[(1, 2),(5, -8)]` is ______

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उत्तर

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अध्याय 1.2: Matrices - Q.3

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If A = `[(4, 3, 2),(-1, 2, 0)]`, B = `[(1, 2),(-1, 0),(1, -2)]`

Find (AB)–1 by adjoint method.

Solution:

AB = `[(4, 3, 2),(-1, 2, 0)] [(1, 2),(-1, 0),(1, -2)]`

AB = [  ]

|AB| =  `square`

M11 = –2  ∴ A11 = (–1)1+1 . (–2) = –2

M12 = –3     A12 = (–1)1+2 . (–3) = 3

M21 = 4       A21 = (–1)2+1 . (4) = –4

M22 = 3       A22 = (–1)2+2 . (3) = 3

Cofactor Matrix [Aij] = `[(-2, 3),(-4, 3)]`

adj (A) = [  ]

A–1 = `1/|A| . adj(A)`

A–1 = `square`


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