Code:
(*lap da thuc noi suy tu 4 diem ban dau nhu sau*)
L = {{1, 17}, {2, 27.5}, {3, 76}, {4, 210.5}};
yiPi[L_, i_] := Module[{t, m, j},
t = 1;
m = 1;
For[j = 1, j ≤ Length[L], j++,
If[i ≠ j,
t = Expand[t (x - L[[j, 1]])];
m *= L[[i, 1]] - L[[j, 1]];
];
];
Return[Expand[L[[i, 2]](t/m)]];
]
Lagrange[L_] := Module[{i, r},
r = 0;
For[i = 1, i ≤ Length[L], i++,
r = Plus[r, yiPi[L, i]];
];
Return[r];
]
Print["P(x)= ", Lagrange[L]];