Let a be a fixed nonzero vector in R^n a. Show that the set S of all vectors x such at ax=0 is a subspace of R^n. b. show that if k is a nonzero real number, then the set A of all vectors x such that ax=k is an affine subspace of R^n, but not a linear subspace. how do i even show this.. im so confused. help please!! thanks.