The server will give you the graph of two functions *f* (x) and g(x),
whose expressions
will be hidden. You will then be presented a certain number of other graphs,
corresponding to functions such as *f* (x)+g(x), *f* (-x)-g(x),
-*f* (x)+g(-x), etc (see the menu below). And you should locate the one
which corresponds to one which will be precised in a question.
To give the reply, you can simply click on the graph which you believe to be
the good one.