$\displaystyle \sin \theta + \cos \theta = \frac{1} {3}$ 일 때, $\displaystyle \frac{\sin \theta \cos \theta} {\left (\sin \theta - \cos \theta \right) ^{{2}}}$ 의 값은?

• ①$\displaystyle - \frac{8} {17}$
• ②$\displaystyle - \frac{4} {17}$
• ③$\displaystyle \frac{4} {17}$
• ④$\displaystyle \frac{8} {17}$