Posted by Megan on .
Two spheres with charges of 4.00nC and 3.00nC are placed 0.500m apart. At what point between the two charges must the third charge of 2.00cN be placed so that the net electrostatic force acting on this charge is zero?

physics 
Elena,
k •q1 •q3/x^2 = k •q2 •q3/(dx)^2
q1 •q3 (dx)^2 = k •q2 •q3• x^2
Solve for x 
physics 
Elena,
The second line
q1 •q3 (dx)^2 = q2 •q3• x^2 
physics 
Megan,
Elena, for some reason I'm getting an answer of 3
(8.00 x 10^12) x (dx)^2 = (6.00 x 10^12) x (x^2)
(dx)^2/x^2 = 7.5 x 10^1
(dx)(dx)/x^2 = 7.50 x 10^1
x^2x+0.25/x^2= 7.50 x 10^1
then I get x = 3
Can you help! I'm not sure where i am going wrong. 
physics 
Elena,
q1 • (dx)^2 = q2 • x^2
4•10^9•(dx)^2 = 3•10^9•x^2
4(d^2  2•d•x + x^2) = 3•x^2,
x^2  4x + 1 = 0
x =2 ± sqrt(41) =2 ± 1.73.
x1 = 0.27 m, x2 =3.73m (falls out)