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Matrices a and B satisfy `AB=B^(-1)`, where `B=[(2,-1),(2,0)]`. Find (i) without finding `B^(-1)`, the value of K for which `KA-2B^(-1)+I=O`. (ii) without finding `A^(-1)`, the matrix X satifying `A^(-1) XA=B`. |
Answer» (i) `AB=B^(-1)` or `AB B=B^(-1)B` or `AB^(2)=I` Now, `KA-2B^(-1)+I=O` or `KAB-2B^(-1)B+IB=O` or `KAB-2I+B=O` or `KAB^(2)-2B+B^(2)=O` or `KI-2B+B^(2)=O` or `K[(1,0),(0,1)]-2[(2,-1),(2,0)]+[(2,-1),(2,0)][(2,-1),(2,0)] =[(0,0),(0,0)]` or `[(K,0),(0,K)]-[(4,-2),(4,0)]+[(2,-2),(4,-1)]=[(0,0),(0,0)]` or `[(K-2,0),(0,K-2)]=[(0,0),(0,0)]` ot `K=2` (ii) `A^(-1)XA=B` or `A A^(-1)XA=AB` or `IXA=AB` or `XAB=AB^(2)` or `XAB=I` or `XAB^(2)=B` or `XI=B` or `X=B` |
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