[SOLVED] Quick Question.....I have the answer with steps, but can't figure out how th 1. The problem statement, all variables and given/known data Two charges of 1.5x10^6C and 3x10^-6C are .20m apart. Where is the electric field between them equal to zero? 2. Relevant equations 3. The attempt at a solution Variables r(total)= .2m q1= 1.5x10^-6 q2=3x10^-6 (r2)^2= (.20 - r1)^2 E1 = E2 kq1/(r1)^2 = kq2/(r2)^2 1.5x10^-6C/(r2)^2 = 3.0x10^-6C/(r2)^2 since (r2)^2 = 2(r1)^2 substitude for (r2)^2 and rearrange: 0= (r1)^2 + .4r1 - 4.0x10^-2 then quadratic forumula...... the part I highlighted where it turns from red to blue, is the step I don't understand. I tried to rearrange it, but it doesn't come out as a quadratic as the book answer does.