Chapter 17.5, Problem 20E

Divergence of radial fields Calculate the divergence of the following radial fields. Express the result in terms of the position vector r and its length |r|. Check for agreement with Theorem 17.10

20. $F=\langle x,y,z\rangle \left(x^2+y^2+z^2\right)=r{\left|r\right|}^2$