I'm a bit lazy to write it down...
all there notions are borrow from the proof of VFSLS in the book.
Here is a full definition
Vector Form of Solutions to Linear Systems
Suppose that [A | b] is the augmented matrix for a consistent linear
system LS(A, b) of m equations
in n variables. Let B be a row-equivalent m * (n + 1) matrix in
reduced row-echelon form. Suppose
that B has r nonzero rows, columns without leading 1's with indices F
= {f_1, f_2, f_3, ...... f_n-r, n+1},
and columns with leading 1's (pivot columns) having indices D = {d_1,
d_2, d_3, .......d_r} Define vectors
c, u_j , 1 <= j <= n - r of size n by
......(these all can be copy from the proof of VFSLS, cause I don't
know how to write something is an object in a set and some set is a
subset to another set)
For LS(A,0), the augment matrix is [A | 0] and each notation of the
corresponding object for it should be with a superscript " ' ", for
example, B' means the row-reduce echelon form of [A | 0], c' means the
constant vector.