param N := 3;

var x{1..N};

minimize f:
sum {i in 1..10} ((exp(-1*i*x[1]/10) - exp(-1*i*x[2]/10)) - x[3]*(exp(-1*i/10) - exp(-1*i)))^2;

data;
var x:=
1	0
2	10
3	20;

solve;

display x;