Question

How do we solve this question​

Answer 1

there are two charge which is +e and -e.

and the magnitude of coulomb force is kq^2/r^2.

so the magnitude of force is

F = ke^2/r^2

if you draw the diagram of this senerio, you see that the direction of force is antiparallel of direction of radius.

so, multiply the magnitude with cap of r or r vector/r.

so the answer is 1 and 3.