What does `(q_(1) + q_(2)) = 0` signify ?

What does q_1+q_2=0 singnify in electrostatics?

What does the quality factor (Q) signify in a LCR a.c. circuit ?

Charges q_(1) = 1.5 mC, q_(2) = 0.2 mC and q_(3) = -0.5 mC , are placed at points A,B,C respectively as shown in Fig. If r_(1) = 1.2m and r_(2) = 0.6m , calculatae magnitude of resultant force on q_(2) .

Give one example of a nuclear reaction. Also define the Q-value of the reaction. What does Q gt 0 signify ?