Let defined in .

Show that the field is irrotational and calculate the general potential of this field.

I've calculated its curl (0), so the field is irrotational.

Now I must find, I believe, a vector field whose curl is . I called it but I've too much unknowns. I don't know how to solve the last part. Can someone help me?

In details I wrote and 2 other relations of the same kind. At last I ended up with at least 9 unknowns and only 3 equations.