Lagrangian Interpolation

[PedroLeiva]

Both altrnatives (0 ENTER Xn) plus Clx STO 5, or (12,5 ENTER -2) gives me the same results as yours: 13.1667. So it works as you suggest. So this is a way to use Lagrangian for linear interpolation (1st. order polynomials), only two points.

For 2nd order polynomials we can use your program, just loading three points; so we cannot use it for 3rd. or 4th. order, considering we will need 4 or 5 points. Am I right?
Pedro