@dharr , @acer Thank you very much.

@nm 
When I add this lines

incr:=solve(diff(f,x)>0,x): 
decr:=solve(diff(f,x)<0,x): 
incr_ltx:=fmt(incr): 
decr_ltx:=fmt(decr):

I got a bug

@sand15 Thank you very much

@vv Thank you very much.

@Kitonum Can you write your answer in the form, e.g  AS=3, BS=13, CS=5, AB=11, AC=7, BC=17?

@vv I am sorry.

@Kitonum Thank you very much

@Carl Love You can restrict each side of each triangle to be integer or not.

@acer Thank you very much. My goal is expand the expression has the form (a + b)^n step by step. 

@acer Thank you very much. Let me try other special cases. 
Is this another question? Can your code use for this cases
(x + 3)^2 = x^2 + 2. (x)*(3) + 3^2 = x^2 + 6 x + 9;
(t- k)^2 = t^2 - 2*t*k + k^2?

@acer Please see this case L := [[1, 2], [-3,1]]; Can I write x instead 1 x or y instead 1 y?

@acer I am sory. Now I can save the file. 

@acer When I copy your code and put the the file in the same folder, I put a new name of the file, when I enter, I get the massage as below. How can I compile to get the results<

@acer Thank you very much.

@acer Can I get latex file in the same folder of the  Maple file instead copy from Maple?