Question 1129414
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The answer from tutor @alex.33 is not right; he has the requirement backwards.<br>
In multiplying matrices, the elements of the rows of the first matrix are multiplied one by one by the elements in the columns of the second matrix.  So the requirement for being able to multiply two matrices is the the number of elements in each ROW of the FIRST matrix be equal to the number of elements in each COLUMN of the SECOND matrix.<br>
Your example meets that requirement: there are 2 elements in each row of the first matrix and 2 elements in each column of the second.<br>
The product matrix is<br>
{{{matrix(2,2,1,2,-1,4)}}} * {{{matrix(2,3,1,-2,3,2,2,-1)}}} = {{{matrix(2,3,1*1+2*2,1*-2+2*2,1*3+2*-1,-1*1+4*2,-1*-2+4*2,-1*3+4*-1)}}} = {{{matrix(2,3,5,2,1,7,10,-7)}}}<br>