Ex 4.5, 18 If A is an invertible matrix of order 2, then det(A−1) is equal to A. det (A) B. 1/(det (A)) C. 1 D. 0 We know that AA-1 = I Taking determinant both sides |"AA−1" |= |I| |A| |A-1| = |I| |A| |A-1| = 1 |A-1| = 1/(|A|) Since |A| ≠ 0 (|AB| = |A| |B|) ( |I| = 1) Hence, |A-1| = 1/(|A|) is valid Thus, the correct answer is B

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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