param N := 3;

var x{1..N};

minimize f:
-1*x[2];

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

subject to cons2:
x[1]^2 + x[2]^2 + x[3]^2 - 1 = 0;

data;
var x:=
1	-0.1
2	-1
3	0.1;
solve;

display x;