I was trying to solve this differential equation:
$$2yy'' + 3y'^2 = 4y^2 $$
And I found this way to solver it: http://eqworld.ipmnet.ru/en/solutions/ode/ode0344.pdf but I don't understand why $w'_y = y''_{xx}$. If $w(y) = (y'_x)^2$, how can I find this:
$$ \dfrac{d}{dy}\bigg(\dfrac{dy}{dx}\bigg)^2$$