1. If the columns of a 7x7 matrix D are linearly independent, what can be said about the solutions Dx=b for a given 7x1 b (where x is 7x1 too)?
   a) Dx=b has at least one solution, but we cannot say anything more about the solution or solutions
   b) Dx=b has a unique solution, but we cannot say anything more about it
   c) Dx=b has a unique solution, and I can tell you what it is
   d) Dx=b has infinite solutions
   e) Dx=b has no solutions for some b and infinite solutions for other b
   
   
   
   
2. If the columns of a 7x6 matrix D are linearly independent, what can be said about the solutions Dx=b for a given b, with x as 6x1 and b as 7x1?
   a) Dx=b has at least one solution, but we cannot say anything more about the solution or solutions
   b) Dx=b always has a unique solution
   c) Dx=b has no solutions for some b and infinite solutions for other b
   d) Dx=b has one solution for some b and no solutions for other b
   e) We can only reason that Dx=b has 0, 1 or infinite solutions as with any linear system.
   
   
   
   
   
   
   1. c) 2. d)