정적분 $\displaystyle \int _ {1} ^ {2} \frac{x^ {2} -1} {x^ {3} +x} d x$ 의 값은?

• ①$\displaystyle {\ln} \left (\frac{5} {4} \right)$
• ②$\displaystyle {\ln} \left (\frac{3} {2} \right)$
• ③$\displaystyle {\ln} \left (\frac{7} {4} \right)$
• ④${\ln} 2$
• ⑤$\displaystyle {\ln} \left (\frac{9} {4} \right)$