1. The problem statement, all variables and given/known data Give examples of methods used to find approx. answers to the Schrödinger's eqn. of systems too complex to be solved analytically. 2. Relevant equations None required. 3. The attempt at a solution I understand there are three methods commonly used, those mentioned in the title and a 3rd, perturbation theory (of which i can explain) however variation and hybridisation have me at a loss. I've tried many internet sources and my local physics library has no books available. From what i understand Variation Theory envolves modifying the wave equations of fundamental systems used to describe a system (fundamental systems being things like the rigid rotor, harmonic oscillator, hydrogen-like atom etc.) Hybridisation however i have less knowledge of, from the name i imagine its something to do with combining states of atoms/molecules.