# The linear variation method

1. Jan 7, 2016

### Morten

In the chapter 9-5 "The Linear Variation Method" p. 363 from the book: Basic Principles and Techniques of Molecular Quantum Mechanics by Ralph Christoffersen, the first thing he does is to minimize the energy, E = cHc/cSc, by requiring its derivative with respect to the coefficient cp* to equal zero. He claims the following expression:
dE/dcp* (cSc) + E d/dcp* (cSc) = d/dcp* (cHc) , whereas, by the quotient rule, I would claim:
((dE/dcp*)(cHc)(cSc) - (cHc) dE/dcp*(cSc)) / (cSc)2 = 0 , am I perhaps wrong?

2. Jan 7, 2016

### Morten

The thing was, Ralph indicated strongly the action of setting the derivate equal to zero in that expression but this was postponed to later on in the book as I just read, that was what confused me. For this I am sorry