@Kitonum Thank you very much but why discrim(Eq,x) returns me "invalid arguments in discrim()" ?

@Kitonum I solved all my problems

@Kitonum Thank you very much, you are a genius bu it doesn't run, i don't understand the function plots:-display... and the final semicolon. Furthermore, it doesn't plot anything of each line, for example, the rectangle gives me :POLYGONS([[0., 0.], [10., 0.], [10., 10.], [0., 10.]], COLOUR(RGB, 1.00000000, 0., 0.), STYLE(LINE), THICKNESS(2))

but there is not the plot

@vv Thank you very much, do you know how can i return separately s and n?

@vv 

Sorry if i hadn't put it but i have initialized all the variables before and i typed wrong lista which is list you're right

I still have the problem!

Thank you very much