Where Along the Y-Axis is the Electric Field Zero?

[Punchlinegirl]

A charge of -4.84 \mu C is located at the origin, and a charge of -6.22 \mu C is located along the y-axis at 1.361 m. The value of the Coulomb constant is 8.99 x 10^9. At what point along the y-axis is the electric field zero. Answer in units of m.
I know that for the electric field to be zero, the electric field on the charges must equal each other.
I called the distance from the charge at the origin R, and the distance from the second point is d-r.
I used the equation for electric field and set them equal to each other.
kQ/r^2= kq/(d-r)^2
Q/r^2 = q/ (d-r)^2
Q(d-r)^2 =qr^2
(d-r)^2 =qr^2/ Q
(d^2 -2dr + r^2)/ r^2 = q/Q
d^2/r^2 - 2d/r +1 = q/Q
At this point I got stuck on how to solve for r, can someone help me?
Thanks in advance.

 

[Pyrrhus]

Here's some help
(d-r)^2 =qr^2/ Q
d-r = r \sqrt{\frac{q}{Q}}