Trying to use symsum, keep getting "undefined variable k" error?

I'm unable to use the symsum function of MATLAB. Every time I run it, I keep getting told that my variable of k is undefined. This is even after I've tried using the examples under "help symsum". What the hell is going on?

[Steven Lord]

Please show the exact code you're trying to execute and the full text of the error message you receive when you execute that code.

[jackie lengs]

here it is:

[jackie lengs]

Nevermind I've managed to solve my problem.

[Karan Gill]

I recommend using the documentation when learning about a function ( http://www.mathworks.com/help/symbolic/symsum.html ) and using the help header only for quick lookups.