L this be a three-dimensional scalar field -nbsp fx y z

Question

Calculus-

Let this be a three-dimensional scalar field

 f(x, y, z) = (1)/(x² + y² + z²) - z

Determine the gradient grad f and the value of |grad f| in spherical coordinates.

Note - The negative "z" is not part of the fraction 1/(x² + y² + z²). It is indeed separate.

So the question would read: fraction -z

Where the fraction is 1/(x² + y² + z²).