$\"\"$

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The first equation is c (AB) \ \

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$\"\"$ \ \

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Multiply the matrix AB elements by 3

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$\"\"$ \ \

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The second equation is $\"\"$ \ \

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Multiply the matrix B elements by 3

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$\"\"$ (Substitute matrix A)

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Multiply columns by rows. \ \

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The solution of equation c(AB) =A(cB) is True.

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