1. Class 12
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Question 1 - CBSE Class 12 Sample Paper for 2019 Boards

Last updated at Oct. 1, 2019 by

Question 1

If A and B are invertible matrices of order 3, |A| = 2, |(AB) -1 | = – 1/6. Find |B|

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

    3. CBSE Class 12 Sample Paper for 2019 Boards

    CBSE Class 12 Sample Paper for 2018 Boards →

Transcript

Question 1 If A and B are invertible matrices of order 3, |๐ด| = 2, |(๐ด๐ต)^(โˆ’1) | = โ€“ 1/6 . Find |๐ต| Theory We know that A A-1 = I So, |A A-1| = |I| |A A-1| = 1 |A| |A-1| = 1 |A-1| = 1/|๐ด| Just for reference, no need to write Given |๐ด| = 2, |(๐ด๐ต)^(โˆ’1) | = โ€“ 1/6 We know that |(๐ด๐ต)^(โˆ’1) | = 1/(|๐ด๐ต|) |(๐ด๐ต)^(โˆ’1) | = 1/|๐ด||๐ต| โˆ’1/6 = 1/(2 ร— |๐ต| ) 2 ร— |๐ต| = โ€“6 |๐ต| = (โˆ’6)/2 |๐‘ฉ| = โ€“ 3

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

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