@Markiyan Hirnyk Thank you so much.

@Markiyan Hirnyk Thank you so much.

I am looking forward to hearing from you.

With the best regards,

MDD

@Markiyan Hirnyk Is there another commands for this? I want test them too.

@Preben Alsholm You are right. But in my study, parameters a, b, c,... can specialize in real number. I want one command that could conclude that when a^13b^17 is none zero then a<>0 and b<>0.

@Carl Love What is your idea about the following example?

false!!!

@Carl Love Thanks I think that the assuming command is better.

@Carl Love Therefore you suggest me to use assuming command in my procedure?

@Carl Love Thanks. I want use from above assume command (Kitonum answer) in my procedure. Can I use at middle of procedure from interface(showassumed= 0) command, automatically?

@Kitonum Thank you so much. When I use your answer and then type 'a' it is appears to form 'a~'. Why this is happen?

@Kitonum When this error is appear usually?

@Kitonum I used from your short procedure in my implementation. In the middle of running of my implementation appears the following error where is related with your short procedure. The error is

"Error, (in unknown) invalid input: `expand/power` uses a 2nd argument, e, which is missing"

In fact at the middle of my implementation the input of your short procedure is

A=

B=

If I use from your short proc for these inputs seperatly, it work correctly but, in the middle of run, when program call your short proc, the above error is appeared. What is problem?

@Kitonum Is this a general method?

@Markiyan Hirnyk But your input is two list. I want C only.

@Kitonum Thanks but I want a general method.

@roman_pearce I want not happend this error in the running of my algorithm. What I have to do?