1. The problem statement, all variables and given/known data Given that we have q1 = -4nC on the y-axis at y=0.60m. q2 on the y-axis at y= -1.20m. What must be the sign and magnitude of q2 be for the net electric field at the origin to be: a. Zero b. 50 N/C 2. Relevant equations E=KQ/R2 3. The attempt at a solution I used: ET = E1 + E2 Since ET = 0 ; rearranging the equation: E1 = - E2 Both K can be cancelled out leaving us with: Q1 / R12 = - Q2 / R22 Then, Q2 = - Q1 (R22) / R12 Substituting the values: Q2 = - (-4x10-9)(1.20m)2 / (0.60m)2 Equals 1.6x10-8 Coulombs, but in my test, my prof corrected and added negative sign on the answer. Am I doing something wrong?