적분 $\displaystyle \int _ {0} ^ {\sqrt {2}} x^ {3} \sqrt {x^ {2} +2} d x$ 의 값은?

• ①$\displaystyle \frac{8} {15} (2+ \sqrt {2})$
• ②$\displaystyle \frac{8} {15} (2- \sqrt {2})$
• ③$\displaystyle \frac{16} {15} (2+ \sqrt {2})$
• ④$\displaystyle \frac{16} {15} (2- \sqrt {2})$