http://www.math.toronto.edu/kergin/236_t1_2.pdf
For number 3(a), I don't get how "any of the last 4 columns are linearly dependent" and how x1 is the basic variable... I thought only the last 2 columns were linearly dependent and the first 3 columns are linearly independent. So I thought there would be 7 basic solutions having basic variables: {x1, x2, x4}, {x1, x2, x5}, {x2, x3, x4}, {x2, x3, x5}, {x1, x2, x3}, {x1, x3, x4}, {x1, x3, x5}.
Can someone please help me understand? I feel like I don't thoroughly get the concept of basic solution no matter how much I read about it.
