what is the right syntax to do step shown in pic ?

hello I have problem with subs function, I want to sub some value in equation shown below in pic. what is the right syntax to do this ? can any one help please.

[John D'Errico]

Bad link.

[Walter Roberson]

Which MATLAB version are you using? And are you using the Symbolic Toolbox, or are you using the MATLAB Connector for Maple? I do have never seen the D(x) notation from the Symbolic Toolbox, but I would expect it from Maple.