Question

Which of the following is not permitted when solving a system of linear equations using matrices?

interchange rows
interchange columns
multiply a row by a constant

Answer 1

If i remember correctly the answer is interchange columns. 

Answer 2

Interchange columns are not permitted when solving a system of linear equations using matrices

Explanation:

when solving a system of linear equations using matrices

We try to get identity matrix using row operations

We can interchange any rows. Rows can be interchanged.

We can also multiply any row by a constant.

But columns cannot be interchanged.

Interchange columns are not permitted when solving a system of linear equations using matrices