@Axel Vogt 

thank you very much.

@Carl Love

thanks anyway

 I got one last question. Do you know any way to get explicit answer? I mean any other kind of Software or Programming language to do that properly.

Regards

@Carl Love 

thanks for your help

The problem still is not solved. when I used the convert function, maple made the problem worse. because the answers which come out, are not functional. I mean, the function "RootOf" apears and then there is a long long set of number and variables.

what should I DO ?

Regards.