Problem $1$

Show that

vec$(grad)(\frac{1}{|(vec(r))-\text{v}\text{e}\text{c}(r^{\text{'}})|})=-\frac{(vec(r))-\text{v}\text{e}\text{c}(r^{\text{'}})}{|(vec(r))-\text{v}\text{e}\text{c}(r^{\text{'}}){|}^3}$

where vec$(grad)$ acts on the components of vec$(r)$