Use the geometric definition of divergence to find div v at

Question

Qusetion: 1. Use the geometric definition of divergence to find div v^→ at the origin, where v^→ = -r^→ . Check that you get the same result using the definition in Cartesian coordinates.

2. (a) Let f(x, y) = axy + ax²y + y³. Find div grad f.

(b) If possible, choose a so that div grad f = 0 for all x, y.