param N := 2;

var x{1..N};
var u{1..3};
param c{1..3};

minimize f:
u[1]^2+u[2]^2+u[3]^2;

subject to cons1{i in 1..3}:
u[i] = c[i] - x[1]*(1-x[2]^i);

data;
var x:=
1	2
2	0.2;

param c:=
1	1.5
2	2.25
3	2.625;
solve;

display x;