1.

If `A ` and `B` are two non-singular matrices which commute, then `(A(A+B)^(-1)B)^(-1)(AB)=`A. `A+B`B. `A^(-1)+B^(-1)`C. `A^(-1)+B`D. none of these

Answer» Correct Answer - A
`(a)` `(A(A+B)^(-1)B)^(-1)(AB)`
`=B^(-1)(A+B^(-1))^(-1)A^(-1)(AB)`
`=B^(-1)(A+B)A^(-1)(AB)`
`=(B^(-1)A+I)A^(-1)(AB)`
`=(B^(-1)A A^(-1)+A^(-1))(AB)`
`=(B^(-1)+A^(-1))(AB)`
`=B^(-1)AB+A^(-1)AB`
`=B^(-1)BA+A^(-1)AB`
`=A+B`


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