For A = [8(3 1 -1 2)], then 14 A −1 is given by

(a) 14 [8(2 -1 1 3)]    (b) [8(4 -2 2 6)]

(c) [8(2 -1 1 -3)]        (d) 2 [8(-3 -1 1 -2)]  

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  1. Class 12
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Transcript

Question 38 For A = [■8(3&1@−1&2)], then 14 A−1 is given by (a) 14 [■8(2&−1@1&3)] (b) [■8(4&−2@2&6)] (c) [■8(2&−1@1&−3)] (d) 2 [■8(−3&−1@1&−2)] We know that A-1 = 1/(|A|) adj A Now, |𝑨| = |■8(3&1@−1&2)| = 3 × 2 – (−1) × 1 = 6 + 1 = 7 So, the correct answer is (B) A =[■8(3&1@−1&2)] Now, adj A = [■8(3&1@−1&2)] = [■8(𝟐&−𝟏@𝟏&𝟑)] Thus, A-1 = 1/(|A|) adj A = 1/7 [■8(2&−1@1&3)] So, 14A-1 = 14 × 1/7 [■8(2&−1@1&3)] = 2 [■8(2&−1@1&3)] = [■8(2 × 2&2 × −1@2 × 1&2 × 3)] = [■8(𝟒&−𝟐@𝟐&𝟔)] So, the correct answer is (B)

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.