param N := 3;

var x{1..N};

minimize f:
9*x[1]^2 + x[2]^2 + 9*x[3]^2;

subject to cons1:
x[1]*x[2] - 1 >= 0;

subject to cons2:
x[2] >= 1;

subject to cons3:
x[3] <= 1;

data;
var x:=
1	1
2	1
3	1;

solve;

display x;