Let A and B be two invertible matrices of order 3×3. If detABAT=8 and detAB−1=8, then detBA−1BT is equal to
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a
1
b
14
c
116
d
16
answer is C.
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Detailed Solution
Given, ABAT=8⇒A∥B∥AT=8 [∵|XY|=|X|Y∣]∴|A|2|B|=8 …(i)∵AT=|A| Also __, we have AB−1=8⇒A∥B−1=8⇒ |A||B|=8 ...(ii)∵|A−1|=|A|−1=1|A|On multiplying Eqs.(i) and (ii) , we get |A|3=8.8=43⇒|A|=4⇒|B|=|A|8=48=12 Now, BA−1BT=|B|1|A||B|=121412=116