Problem: Two different point charges $Q_1$ and $Q_2$ are a distance $a$ away from each other. The point charges are both positive. Where is the electric field zero?

So far, I've found the total electric field for a point on the x-axis (assuming $Q_1$ is in the origin, and $Q_2$ is at (a,0)), by using Coulombs law and superposition. This gives me

$E_{tot} = E_1 + E_2 = k\left(\frac{Q_1}{x^2}-\frac{Q_2}{(x-a)^2}\right)\hat{x}$

Then setting $E_{tot} = 0$ and trying to solve for $x$. Now this is where I'm stuck, and even trying to use tools to solve for $x$ I don't arrive at anything similar to the answer which is

"On the line between the charges, $\frac{a}{1+\sqrt{\frac{Q_2}{Q_1}}}$ from the charge $Q_1$"

Am I using the correct method and just need to keep trying to solve for $x$, or am I missing something?

Problem: Two different point charges $Q_1$ and $Q_2$ are a distance $a$ away from each other. The point charges are both positive. Where is the electric field zero?

So far, I've found the total electric field for a point on the x-axis (assuming $Q_1$ is in the origin, and $Q_2$ is at (a,0)), by using Coulombs law and superposition. This gives me

$E_{tot} = E_1 + E_2 = k\left(\frac{Q_1}{x^2}-\frac{Q_2}{(x-a)^2}\right)\hat{x}$

Then setting $E_{tot} = 0$ and trying to solve for $x$. Now this is where I'm stuck, and even trying to use tools to solve for $x$ I don't arrive at anything similar to the answer which is

On the line between the charges, $\frac{a}{1+\sqrt{\frac{Q_2}{Q_1}}}$ from the charge $Q_1$

Am I using the correct method and just need to keep trying to solve for $x$, or am I missing something?