The Symmetric Positive Definite Matrix Again

Another approach to the solution of linear equations (and in fact nonlinear ones) is the method of substitution. Here, one of the unknowns x_k is chosen and one of the equations in which it has a non-zero coefficient is used to generate an expression for it in terms of the other x_j, j ≠ k, and b . For instance, given (2.2) A x = b https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315139784/ed4048a6-e22b-4325-b5dd-51851ea3ba32/content/eq381.tif"/>