Final answer:
Matrix A with three pivot positions means Ax = 0 only has the trivial solution, and Ax = b will have at least one solution for any given b because A is invertible and its columns span the entire three-dimensional vector space.
Step-by-step explanation:
The question pertains to linear algebra and the solutions to systems of linear equations represented in matrix form. Specifically, we are dealing with a 3x3 matrix A which has three pivot positions.
(a) If matrix A has three pivot positions, it means that A is of full rank, and thus, the equation Ax = 0 only has the trivial solution, x=0. There are no free variables, and as a result, there are no nontrivial solutions to this homogeneous equation.
(b) Since A is a 3x3 matrix with three pivot positions, it is invertible, which implies that the equation Ax = b has exactly one solution for every possible b. This is because the columns of A span ℝ^3, the entire space of 3-dimensional vectors, ensuring that every b in ℝ^3 can be expressed as a combination of these columns.