# Linear Algebra-Linear Spaces

## Homework Statement

Are the 3X3 matrices A such that vector <1,2,3> is in the kernel of A, a subspace of R^(3X3)?

## The Attempt at a Solution

I know that the kernel condition gives a subset V={A|A*<1,2,3>=0} but im not sure of how to proceed to show it is in fact a subspace. Should I try to see if it spans or use the definition of a subspace? i'm just confused on how to proceed with the next step