곡선 $\displaystyle y= \frac{x^ {4}} {16} + \frac{1} {2 x^ {2}} (1 \leq x \leq 2)$ 의 길이는?

• ①$\displaystyle \frac{5} {4}$
• ②$\displaystyle \frac{21} {16}$
• ③$\displaystyle \frac{11} {8}$
• ④$\displaystyle \frac{23} {16}$
• ⑤$\displaystyle \frac{3} {2}$