Hi I'm trying to solve a separable DE with a worked solution.
Question: $y′ = (y−9x)^2$
Part of the Given Solution: Letting $v = y − 9x$ becomes $\frac{dv}{dx} = v(x)^2 − 9$
I get that $\frac{dv}{dx} = \frac{dy}{dx} - 9$ but how does the $\frac{dy}{dx}$ become a $v(x)^2$
Thanks