Question 17 - CBSE Class 12 Sample Paper for 2022 Boards (MCQ Based - for Term 1) - Solutions of Sample Papers and Past Year Papers - for Class 12 Boards

Last updated at May 29, 2023 by Teachoo

Given that A = [𝑎𝑖𝑗] is a square matrix of order 3 × 3 and |A| = −7, then the value of ∑_(i=1)
^{
3
}
a
_{
i2
}
A
_{
i2
}
" , where 𝐴
_{
𝑖𝑗
}
denotes the cofactor of element 𝑎𝑖𝑗 is:

(a) 7 (b) −7 (c) 0 (d) 49

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Question 17 Given that A = [𝑎𝑖𝑗] is a square matrix of order 3 × 3 and |A| = −7, then the value of ∑_(𝑖=1)^3▒"𝑎𝑖2𝐴𝑖2 " , where 𝐴𝑖𝑗 denotes the cofactor of element 𝑎𝑖𝑗 is: (a) 7 (b) −7 (c) 0 (d) 49
Now,
= 𝒂_𝟏𝟐 𝑨_𝟏𝟐+𝒂_𝟐𝟐 𝑨_𝟐𝟐+𝒂_𝟐𝟐 𝑨_𝟏𝟐
= Sum of product of elements of Row R2 with its corresponding cofactors
= Determinant of A
= |A|
= 7
So, the correct answer is (B)

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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