Hello, i have problem, can someone help me with PTC Mathcad Prime 11.0.0.0?

See how operators work - "Conditional Operators" from the "Help Center": https://support.ptc.com/help/mathcad/r10.0/en/index.html#page/PTC_Mathcad_Help/conditional_operators.html 

Here's an alternative approach (notice that, for the x-values you use, the condition is always false):

Hi @DV_13990037,

I wanted to see if you got the help you needed.

If so, please mark the appropriate reply as the Accepted Solution or please feel free to detail in a reply what has helped you and mark it as the Accepted Solution. It will help other members who may have the same question.

Of course, if you have more to share on your issue, please pursue the conversation.

Thanks,