First Order ODE/x dy = (y + x^2 + 9 y^2) dx

Theorem
The first order ODE:
 * $(1): \quad x \rd y = \paren {y + x^2 + 9 y^2} \rd x$

has the solution:
 * $\map \arctan {\dfrac {3 y} x} = 3 x + C$