My fault, I should have made this clearer,

Given that you can get down to this equation,

Then multiplying all the terms (both on the left hand side and the right hand side) by

gives

Then, by expanding the bracket out, you get

Now, by standard rules of indices,

and

we get

Then

which can be written as

[1] by collecting the

terms and bringing the 2y term to the left hand side

Now, say you let W be

, just to show this is like a quadratic, you can rewrite [1] as

which is in the general formula for solving a quadratic equation, with roots at

(since

)

(by dividing by 2)

thus

and taking the log of both sides gives

and the rest carries on above

*The formula for solving a quadratic equation in general is as follows in case you can't remember,

for

then