Solution to task 309 from Chertov´s for extramural stud

Solution to task 309 from Chertov´s for extramural stud

309. At the distance a = 20 cm there are two point charges: Q1 = -50 nC and Q2 = 100 nC. Determine the force F acting on the charge Q3 = -10 nC, remote from both charges at the same distance equal to d.