Question 148512
Remember, in order to multiply matrices, the number of columns of the first matrix <font size=4><b>must</b></font> equal the number of rows in the second matrix. So 


{{{(matrix(2,3,1,4,1,3,-6,2))*(matrix(1,2,4,1))}}}


is <font size=4><b>not</b></font> defined since the number of columns of the first matrix is 3 and the number of rows in the second matrix is 1.