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If M is the matrix `[(1,-3),(-1,1)]` then find matrix `sum_(r=0)^(oo) ((-1)/3)^(r) M^(r+1)` |
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Answer» Let `N=M-M^(2)/3+M^(3)/9-M^(4)/27 +...` `:. -(MN)/(3) =- M^(2)/3+M^(3)/9-M^(4)/27 ... oo` Subtracting, we get `N+(MN)/3=M` `implies (I+M/3) N=M` `implies (3I+M)N=3M` `implies N=[(3,-9),(-3,3)][(4,-3),(-1,4)]^(-1)` `=1/13 [(3,-9),(-3,3)][(4,-3),(-1,4)]^(-1)` `=1/13 [(3,-27),(-9,3)]` `=3/13 [(1,-9),(-3,1)]` |
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