1.

Find the matrix X so that `X[[1, 2, 3],[ 4 ,5, 6]]`= `[[-7,-8,-9],[2,4,6]]`

Answer» With the given equation, `X` should be a `2xx2` matrix.
Let `X = [[a,b],[c,d]]`
Then, `[[a,b],[c,d]] [[1,2,3],[4,5,6]] = [[-7,-8,-9],[2,4,6]]`
`=>[[a+4b,2a+5b,3a+6b],[c+4d,2c+5d,3c+6d]] = [[-7,-8,-9],[2,4,6]]`
`:. a+4b = -7->(1)`
`2a+5b = -8->(2)`
`3a+6b = -9=> a+2b = -3->(3)`
`c+4d = 2->(4)`
`2c+5d = 4->(5)`
`3c+6d = 6 => c+2d = 2->(6)`
Subtracting (3) from (1),
`2b = -4=> b = -2`
`=>a+4(-2) =-7 => a = 1`
Similarly, subtracting (6) from (4),
`2d = 0=> d = 0`
`c+4(0) = 2 => c = 2`
So, `X = [[1,-2],[2,0]]`


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