Of course you can set "bounds" on the variables. But no, you are wrong that they must all be the same value. If x is the unknown vector, say of length 2 in this case, say we wanted the lower bound on x(1) to be zero, and x(2) will be unbounded from below. Then the lb argument in this case would be:
lb = [0,-inf];
Similarly, suppose we had upper bounds on x of 10 for x(1), and 5 for x(2).
ub = [10,5];
You can set the bounds to be any values you like of course. They need not all be the same. As you can see, if a variable has no lower or upper bound, then use -inf or +inf respectively.
