https://s0.wp.com/latex.php?latex=%5Cdisplaystyle+F_1%3D%5Cfrac%7B1%7D%7B4%5Cpi%5Cepsilon_0%7D%5Cfrac%7Bqq_1%7D%7B%5Clvert+r_1%5Crvert%5E3%7Dr_1&bg=e6e6e6&fg=333333&s=0&c=20201002