Multiple Choice: If $x^{2} − 2xy = 8$, then when $x = 2$, $\frac{dy}{dx}=$

1. $−\frac{1}{2}$

2. $\frac { 1 } { 2 }$

3. $\frac { 3 } { 2 }$

4. $−\frac{3}{2}$

5. undefined

   Hint:

   the derivative might have both $x$ and $y$ variables in it.
   So be prepared for the final step: you will need to know what y-variable corresponds with $x = 2$ on the given graph.