Thank you guys! you are awesome :D

I think Carle Love nailed it :D but I still have a problem :( and here is the thing:

What I have is an expression  F=a_i * X^i,  i=1:7,   in which  a_i= a_i(y1, y2,y3,....,yn)  and what I am doing is generating Matlab Code with the comand Matlab(a_i) and I import it to Matlab to solve my F in Matlab as a polynomial equation with roots(F) , but after starting to solve it want to make sure that the fact of importing an expression from maple to matlab doesn't effect anything, for that I did the following:

I evaluate F for given (y1,y2,y3.....) and X in Maple and then I do the same in Matlab but I get two different  values!!!

This time I didn't use the function simplify to avoide what Marc Love described.

Does that maen anything to you guys?

Thanks in advance