I Can E(M,K) = C Replace Ek(M) = C in Cryptography Notation?

[Teachme]

I was just reading a cryptography book and have a question about something the author states I highlighed the statement in yellow and included a pictures.
So I was wondering if the function could be written as E(M,K) = C instead of E_k(M)=C since the fact that E is dependent on K. If not why couldn't you write it as this?

Thanks

 

[mathman]

Attached file is unreadable.

 

[Teachme]

Sorry thanks,
here is fixed pic

 

[mathman]

It is more a matter of style than anything else.