the electric field due to a charge 'q' at a distance 'r' is given by
E = q/r
Now, we shall calculate electric field at a point due to each charge individually and then use the principal of super position and add these results to find the net electric field at the point. This can be done for any number of charges.
q1 = 6.5 uC
q2 = -9.2 uC
At x = -4cm
r = 4cm
r2 = 14cm
[tex]E = \frac{1}{4.\pi.e} .[q1/r1^2 + q2/r2^2][/tex]
E = 0.3229 N/C
Similarly at x = -4cm
r1 = 4cm
r2 = 6cm
E = 0.135 N/C