A particle is moving with velocity $\vec { v } = K ( y \hat { i } + x \hat { j } )$, where $K$ is a constant. The general equation for its path is\\
(1) $y = x ^ { 2 } +$ constant\\
(2) $y ^ { 2 } = x +$ constant\\
(3) $x y =$ constant\\
(4) $y ^ { 2 } = x ^ { 2 } +$ constant