@Thomas Richard Thanks a lot, collect(expr,ln) was exactly what I needed !

@acer 

Thanks, it works well with ans3 := subsindets(ans1,`+`,u->U(u)); !

I didn't manage to make the first solution work though.

Ok, thanks !

But in fact I have a lot of terms.

That gives my expression, do I need to type your solution for each of my term :

a:=-2*b1*b2+b2^2+b1^2;  ``(factor(a));

algsubs(a=%, A);

Or is there another way to prevent the disclosure from start? I tried `` before every instruction but it doesn't work.

Thanks a lot to both of you. It works well !

What about (a+b)^2 being a^2 + b^2 +2*a*b ? I want it to stay (a+b)^2.

Out of subject: How do you write math code in the forum ? When I try Maple Math and enter a+b it says "You have entered an invalid Maple expression".