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Find AB and BA, if possible. A = [3. -5] B = [4, 0, -2]````       [1, -3, 2] 

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clairele | eNotes Newbie

Posted May 22, 2013 at 5:32 AM via web

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Find AB and BA, if possible.

A = [3. -5]

B = [4, 0, -2]````

      [1, -3, 2] 

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llltkl | College Teacher | Valedictorian

Posted May 22, 2013 at 6:27 AM (Answer #1)

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Two matrices C and D can be multiplied only if number of columns in C is same as number of rows in D.

Here A is a [1×2] matrix, B is [2×3].

Hence the product AB will be a [1×3] matrix.

Applying the rules of matrix multiplication,

AB =`[[3*4+(-5)*1,3*0+(-5)*(-3),3*(-2)+(-5)*2]]`

= `[[12-5,0+15,-6-10]]`

= `[[7,15,-16]]`

=>answer

In order to find BA, B is a [2×3] matrix, hile A is [1×2].

Number of columns in B is 3, number of rows in A is 1.

Therefore this multiplication can not be done. In other words the product BA will be undefined.

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