Your Help is greatly appreciated. Thanks in advance. I am having a hardtime with these three problems.

1) Find the basis for Nullspace of A if A equals

1 2 -3

2 1 0

-2 -1 3

2) Let W be the subspace of R^(4) spanned by vectors (1,-2,5,3)^(T),

(2,3,1,-4)^(T), (3,8,-3,-5)^(T).Extend the basisof W to a basis of the whole space of R^(4).