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If M is a matrix of order 3X3 such that MMT=I and det (M)=1 then detMI=

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detailed solution

Correct option is C

We have |M-I|=M-MMT                             =MI-MT                             =|M|I-MT                             =|(I-M)T| ∵M=1and IT=I                             =|(I-M)|    ∵AT=A                            =(-1)3|M-I|.           ∴ M-I=-|M-I|.⇒2|M-I|=0.⇒|M-I|=0.


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