If A = [8(1 -1 0 2 3 4 0 1 2)] and B = [8(2 2 -4 -4 2 -4 2 -1 5)], then
(a) A−1 = B          (b) A−1 = 6B 
(c) B−1 = B          (d) B−1 = 1/6 A

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  1. Class 12
  2. Solutions of Sample Papers and Past Year Papers - for Class 12 Boards

Transcript

Question 25 If A = [■8(1&−1&0@2&3&4@0&1&2)] and B = [■8(2&2&−4@−4&2&−4@2&−1&5)], then (a) A−1 = B (b) A−1 = 6B (c) B−1 = B (d) B−1 = 1/6 A Let’s try multiplying AB AB = [■8(1&−1&0@2&3&4@0&1&2)] [■8(2&2&−4@−4&2&−4@2&−1&5)] = [■8(2+4+0&2−2+0&−4+4+0@4−12+8&4+6−2&−8−12+20@0−4+4&0+2−2&0−4+10)] = [■8(6&0&0@0&6&0@0&0&6)] = 6[■8(1&0&0@0&1&0@0&0&1)] = 6I Thus, AB = 6I 𝟏/𝟔 AB = I So, we can say B−1 = 𝟏/𝟔 A So, the correct answer is (D)

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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.