We have:
[tex]3xm+2ym-2yn-3xn=0\\\\(3x+2y)m-(2y+3x)n=0\\\\(3x+2y)m-(3x+2y)n=0\\\\(3x+2y)(m-n)=0\\\\\\3x+2y=0\qquad\vee\qquad m-n=0\\\\2y=-3x\quad|:2\qquad\vee\qquad m=n\\\\\\y=-\dfrac{3x}{2}\qquad\vee\qquad m=n[/tex]
but we know, that [tex]m\neq n[/tex] so the answer is:
[tex]\boxed{y=-\dfrac{3x}{2}}[/tex]
