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if `A` and `B` are two matrices of order `3xx3 `so that `AB=A` and `BA=B` then `(A+B)^7=`A. `7(A+B)`B. `7. I_(3xx3)`C. `64 (A+B)`D. `128 I` |
Answer» Correct Answer - C `AB=A, BA=B` `ABA=A^(2)` or `A(BA)=A^(2)` or `A=A^(2)` Similarly, `B^(2)=B` `(A+B)^(2)=A^(2)+B^(2)+AB+BA` `=A+B+A+B=2(A+B)` `(A+B)^(3)=(A+B)^(2) (A+B)=2(A+B)^(2)=2^(2) (A+B)` `implies (A+B)^(7)=2^(6)(A+B)=64 (A+B)` |
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