The velocity components in the $x$ and $y$ directions for an incompressible flow are given as $u = (-5 + 6x)$ and $v = -(9+6y)$, respectively. The equation of the streamline is

1. $(-5+6x)-(9+6y) = \text{constant}$
2. $\dfrac{-5+6x}{9+6y}= \text{constant}$
3. $(-5+6x)(9+6y) = \text{constant}$
4. $\dfrac{9+6y}{-5+6x}= \text{constant}$