mRow takes three arguments: an expression, a matrix A and an
integer n.
mRow returns the matrix obtained by replacing in A, the row of index
n by the product of the row of index n by the expression.
Input:
Output:
The scale (or SCALE) command is the same as
mRow except that it takes the arguments in a different order;
the matrix comes first, then the expression, then the integer.
Input:
Output: