param N:= 21;
param x{i in 1..N} := (i-1)/(N-1);
param y{i in 1..N} := exp(x[i]); 

var a;
var b;
var c;

minimize f: sum {i in 1..N} (y[i]-(a*x[i]^2 + b*x[i] + c))^2;