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`A=[(3,a,-1),(2,5,c),(b,8,2)]` is symmetric and `B=[(d,3,a),(b-a,e,-2b-c),(-2,6,-f)]` is skew-symmetric, then find AB. |
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Answer» Correct Answer - `AB=[(-4,3,-6),(-31,54,-26),(-28,9,-50)]` A is symmetric `implies A^(T)=A` `implies [(3,2,b),(a,5,8),(-1,c,2)]=[(3,a,-1),(2,5,c),(b,8,2)]` `implies a=2, b=-1, c=8` B is skew-symmetric `implies B^(T)=-B` `implies [(d,b-a,-2),(3,e,6),(a,-2b-c,-f)]=[(-d,-3,-a),(a-b,-e,2b+c),(2,-6,f)]` `implies d=-d, f=-f` and `e=-e` `implies d=f=0` So `A=[(3,2,-1),(2,5,8),(-1,8,2)]` and `B=[(0,3,2),(-3,0,-6),(-2,6,0)]` `implies AB=[(3,2,-1),(2,5,8),(-1,8,2)][(0,3,2),(-3,0,-6),(-2,6,0)]` `=[(-4,3,-6),(-31,54,-26),(-28,9,-50)]` |
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