OK I think I've found something that fixes my problem with this question.
I wrote the problem down wrong! This kind of makes sense to me now.
Find all points at which the direction of fastest change of is
So I think the question is asking me to find the points in such that
The text is saying all points on work. i'm only getting the one point .
While is on something like (2,3) is on but the gradient at that point is which isn't equal to ?
Would someone care to explain to me what I'm doing wrong?