Consider the sets of vectors of the following form. Determine whether the sets are subspaces of R3. If a set is a subspace, give a basis and its dimension. (Enter your basis as a comma-separated list. Enter each vector in the form (x1, x2, ...). If a set is not a subspace, enter NA for its basis and dimension.)
How do I go about this last one?
(c) (a, b, 4) basis NA dimension NA
(d) (a, a, a + 5) (1.16)x basis dimension1