I'd like to know how to solve a cubic and quartic equation by Lagrange's method. In the wiki (

http://en.wikipedia.org/wiki/Quadrat...nge_resolvents,

http://en.wikipedia.org/wiki/Cubic_e...nge.27s_method,

http://en.wikipedia.org/wiki/Quartic...ange_resolvent) there is the method for solve those equations, but, not appears truly a methodical method, appears that in each page the equation are solving of a different way. I'd like of a formula, a step-by-step, for the lagrange's method. You can help me?