2.1 Vectors and Linear Equations

2.2 The Idea of Elimination

2.3 Elimination Using Matrices

2.4 Rules for Matrix Operations

2.5 Inverse Matrices

If $A$ is invertible, then $Ax = 0$ can only have the zero solution $x = A^{-1}0 = 0$

2.6 Elimination = Factorization: A = LU