How Do You Solve This Directional Derivative Problem?

[sarahisme]

Hello,

I am confused in as how to do this question :S... any help, pointers etc. would be great.

http://img87.imageshack.us/img87/637/picture4nd7.png

Thanks

sarah :)

 

[quantumdude]

Please show how you started and where you got stuck. Thanks.

 

[sarahisme]

will post it later, though i may be on the verge of a breakthrough! :D