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If A = [123115247], then find the value of a31A31 + a32A32 + a33A33. - Mathematics and Statistics

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प्रश्न

If A = `[(1, 2, 3),(1, 1, 5),(2, 4, 7)]`, then find the value of a31A31 + a32A32 + a33A33.

योग

उत्तर

We have,

A = `[(1, 2, 3),(1, 1, 5),(2, 4, 7)]`

a31 = 2, a32 = 4, a33 = 7

A31 = `|(2, 3),(1, 5)|` = 10 - 3 = 7

A32 = `- |(1, 3),(1, 5)|` = - (5 - 3) = - 2

A33 = `|(1, 2),(1, 1)|` = 1 - 2 = - 1

∴ a31A31 + a32A32 + a33A33 

= 2(7) + 4(-2) + 7(-1)

= 14 - 8 - 7 

= - 1

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