21. a. In some cases, a matrix may be row reduced to more

than one matrix in reduced echelon form, using different

sequences of row operations.

b. The row reduction algorithm applies only to augmented

matrices for a linear system.

c. A basic variable in a linear system is a variable that

corresponds to a pivot column in the coefficient matrix.

d. Finding a parametric description of the solution set of a

linear system is the same as solving the system.

e. If one row in an echelon form of an augmented matrix

is [0 0 0 5 0], then the associated linear system is

inconsistent.