Problem 1
The second column is twice the first, so Col(A)=span{(1,3)}.
Faculty use
Column Space and Solvability
Reward correct mathematics, explicit dimensions/hypotheses, interpretation, and verification. Equivalent valid reasoning should receive credit.
Problem 2
The dimension of the column space, equivalently the number of independent output directions.
Problem 3
Definitions should identify the vector/matrix/space/transformation, dimensions or domain/codomain, and the hypotheses behind identifying all attainable outputs of a matrix. Use the formulas Col(A)={Ax:x∈Rⁿ}; Ax=b solvable iff b∈Col(A).
Problem 4
A strong error analysis identifies the first step that violates a definition, dimension, theorem hypothesis, or matrix-operation rule; then repairs that step and re-verifies the final result.
Problem 5
Application responses vary. Require defined variables, a compatible matrix/vector model connected to solution structure, function approximation, matrix spaces, networks, and abstract modelling, a complete computation, interpretation, and limitations.
Problem 6
Accept two independent checks appropriate to the task: reconstruction, residual, RREF comparison, determinant/rank test, orthogonality, substitution, eigenpair check Av=λv, factorization product, or a second method.
Scoring guidance
Six problems × 10 points: 5 mathematical accuracy, 2 structure/justification, 2 verification/interpretation, 1 notation and communication.