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Using Cofactors of elements of third column, evaluate Δ = |(1,x,yz),(1,y,zx),(1,z,xy)|. - Mathematics

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Question

Using Cofactors of elements of third column, evaluate Δ = `|(1,x,yz),(1,y,zx),(1,z,xy)|`.

Evaluate
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Solution

Δ = `|(1,x,yz),(1,y,zx),(1,z,xy)|`

A13 = `-1^(1 + 3) |(1,y),(1,z)|`

= (1) (y − z)

= (y − z)

A23 = `-1^ (2 + 3) |(1,x),(1,z)|`

= (−1) (x − z)

= (z − x)

A33 = `-1^(1 + 3) |(1,x),(1,y)|`

= (1) (x − y)

= (x − y)

Δ = a13A13 + a23A23 + a33A33

= yz(y − z) + zx(z − x) + xy(x − y)

= y2z − yz2 + z2x − zx2 + x2y − xy2

= x2y + y2z + z2x − xy2 − yz2 − zx2

= (x2y − xy2) + (y2z − yz2) + (z2x − zx2)

= xy(x − y) + yz(y − z) + zx(z − x)

= (x − y)xy + (y − z)yz + (z − x)zx

= (x − y)(y − z)(z − x)

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Chapter 4: Determinants - Exercise 4.4 [Page 126]

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NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 4 Determinants
Exercise 4.4 | Q 4 | Page 126

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