Note these are essentially interpolation formulae for if one uses information from m t values, you can fit a degree m-1 polynomial |
Taylor expansion and Polynomial fitting are essentially the same thing! |
Implicit Multistep Methods are gotten using backwards difference interpolating polynomials starting at ti+1. But wherever we we need f(ti+1,y(ti+1)), we use f(ti+1, X*i+1) where X*i+1is derived from the explicit predictor equation |
Note that implicit formulae should be best as explicit method involves extrapolation from ti to ti+1 whereas in implicit case ti+1 is endpoint of region in which interpolation done |
Extrapolation is always unreliable and to be avoided! |