Question Number 104486 by Anindita last updated on 21/Jul/20

If A =  [(3,(−4),2),((−2),1,0),((−1),(−1),1) ]and   B =  [(1,2,(−2)),(2,5,(−4)),(3,7,(−5)) ]then   show that AB = BA = I_3  .

Answered by OlafThorendsen last updated on 21/Jul/20

Just calculate B^(−1)  = (1/(detB))cov(B)^T   Then B^(−1)  = A  ⇒ AB = B^(−1) B = I_3  = BB^(−1)  = BA