《Introduction to Linear Algebra, Fourth Edition》的原文摘录
we needed to open linear algebra to the world (查看原文 )
Let me connect these special matrices A and S to calculus. The vector
x changes to a function x(t). The differences Ax become the derivative dx/ dt = bet). In
the inverse direction, the sum Sb becomes the integral of bet). (查看原文 )
When E multiplies on the right, it acts on the columns of A. (查看原文 )
Schur complement. (查看原文 )
To solve A x = b without A-I, we deal with one column b to find one column x. (查看原文 )
Suppose there is a nonzero vector x such that Ax = 0 (查看原文 )
A triangular matrix is invertible if and only if no diagonal entries are zero. (查看原文 )
The column space C (U) consists of
all vectors of the form (b I , b2 , b3 , 0). (查看原文 )
The same column of A can't be a combination of earlier
columns, because Ax = 0 exactly when Rx = O. (查看原文 )
The square matrix AT A is invertible when the rank is n (查看原文 )
My choice for Xp would be (1,0). (查看原文 )
The point is, our definition doesn't pick out one particular vector as gUilty. All columns of A are treated the same (查看原文 )
This V is the nullspace of any m by 3 matrix B of rank 1, if every row is a multiple
of (0, 0,1). (查看原文 )
The pivot columns of A are a basis for its column space... (查看原文 )
recursive least squares (查看原文 )
Then ATA, with this same nullspace, is invertible. (查看原文 )
You may think that projection onto the whole space is not worth mentioning. (查看原文 )