Xy dng spline bc 3 bin t nhin:

Vi spline bc ba bin t nhin th v

Ta c:

Ma trn Splinetm : Suy ra ma trn tm f, n

Ghi ra nhp cc gi tr X;YT suy ra cc gi tr sau:

Th vo cc biu thc sau tm cc h s: (phng trnh bc nht)

T suy ra cc gi tr cn tnh