Please, can someone give me a hand? I can not understand why in the first case the collect command does not work while the second one works correctly. Many thanks for your attention.trasformaziione_equazioni1.mw
 

Download trasformaziione_equazioni1.mw

I can not understand why the following statement works perfectly:
with (plots);
P1: = plot (f (x), x = xmin .. xmax, y = ymin .. ymax, color = "green");
P2: = plot (orddir, x = xmin .. xmax, y = ymin .. ymax, color = "blue");

Plots [display] (plottools [line] ([ascf, ymin], [ascf, 10]), color = red;
Plot ([5, y, y = 0 .. 10]);
P3: = implicit plot (x = ascf, x = xmin .. xmax, y = ymin .. ymax, color = red, linestyle = 3, thickness = 2);
P4: = plot (points, x = xmin .. xmax, y = ymin .. ymax, style = point, symbol = circle, symbolsize = 20, color = "black");
P5: = plot (h, x = xmin .. xmax, y = ymin .. ymax, color = "yellow");
Display ({p1, p2, p3, p4, p5}, axes = normal, scaling = unconstrained, title = "Parallel, vertice, focus, direction and axis of symmetry", gridlines = true);

While in the following
Points: = [F, V, A, B];
with (plots):
P1: = plot (f (x), x = xmin .. xmax, y = ymin .. ymax, color = "green");
P2: = plot (yd, x = xmin .. xmax, y = ymin .. ymax, color = "blue");
P3: = implicitplot (x = xv, x = xmin .. xmax, y = ymin .. ymax, color = red, linestyle = 3, thickness = 2);
P4: = plot (points, x = xmin .. xmax, y = ymin .. ymax, style = point, symbol = circle, symbolsize = 20, color = "black");

Do (% Plot0 = display ({p1, p2, p3, p4}, axes = normal, scaling = unconstrained, title = "Parallel, vertices, focus, direction and axis of symmetry", gridlines = true));

P4 does not print anything. In thanking you for the kind attention, I cordially greet you. Carmine Marotta ..

I'm new to mapleprimers and if I make some mistakes I apologize. 

The problem I ran and on which I ask for help is that the command of maple latex I results in latex only the result of an arithmetic expression and the expression does not translate into latex itself. for example, the command latex (3 + 2) I 5 and not as a result from the translation in latex of 3 + 2. I also tried using the command inetrt form but did not succeed, I tried it with the quotes '' and even succeed. I also tried it with double quotes and with simple expressions funzioa eg latex ("(3 + 2) * 5") from me as a result `` (3 + 2) * 5 '' but with more complex expressions: eg. latex("\""(2+1/(5))^(0)+(6/(9)*(((83-8)/(90))-15/(10)+(3/(9))/(2)) -6/(9))/(75/(100)*12/(9))"''") mi da 

Error, Got internal error in Typesetting:-Parse:-Postprocess : "internal error: invalid object ""

Thanking for the help, Best regards