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2.4 Homogeneous Systems                                                             63

                                    2.4.5. Suppose that A is the coefficient matrix for a homogeneous system of
                                           four equations in six unknowns and suppose that A has at least one
                                           nonzero row.
                                              (a) Determine the fewest number of free variables that are possible.
                                              (b) Determine the maximum number of free variables that are pos-
                                                  sible.

                                    2.4.6. Explain why a homogeneous system of m equations in n unknowns
                                           where m<n must always possess an infinite number of solutions.


                                    2.4.7. Construct a homogeneous system of three equations in four unknowns
                                           that has
                                                                    −2          −3
                                                                                
                                                                   1         0 
                                                                      0   + x 4   2  
                                                                x 2 
                                                                      0          1
                                           as its general solution.

                                    2.4.8. If c 1 and c 2 are columns that represent two particular solutions of
                                           the same homogeneous system, explain why the sum c 1 + c 2 must also
                                           represent a solution of this system.
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