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If `A=[(1,-1),(2,1)], B=[(a,1),(b,-1)]` and `(A+B)^(2)=A^(2)+B^(2)+2AB`, thenA. `a=-1`B. `a=1`C. `b=2`D. `b=-2` |
Answer» Correct Answer - A::D Given, `(A+B)^(2)=A^(2)+B^(2)+2AB` or `(A+B) (A+B)=A^(2)+B^(2)+2AB` or `A^(2)+AB+BA+B^(2)=A^(2)+B^(2)+2AB` or `BA=AB` or `[(a,1),(b,-1)] [(1,-1),(2,1)]=[(1,-1),(2,1)][(a,1),(b,-1)]` or `[(a+2,-a+1),(b-2,-b-1)]=[(a-b,1+1),(2a+b,2-1)]` The corresponding elements of equal matrices are equal. `a+2=a-b, -a+1=2 implies a=-1` `b-2=2a+b, -b-1=1implies b=-2` `implies a=-1, b=-2` |
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