8.
下列结论:\(①\)数列\( \sqrt {2}, \sqrt {5},2 \sqrt {2}, \sqrt {11}…\),的一个通项公式是\(a_{n}= \sqrt {3n-1}\); \(②\)已知数列\(\{a_{n}\}\),\(a_{1}=3\),\(a_{2}=6\),且\(a_{n+2}=a_{n+1}-a_{n}\),则数列的第五项为\(-6\); \(③\)在等差数列\(\{a_{n}\}\)中,若\(a_{3}+a_{4}+a_{5}+a_{6}+a_{7}=450\),则\(a_{2}+a_{8}=180\); \(④\)在等差数列\(\{a_{n}\}\)中,\(a_{2}=1\),\(a_{4}=5\),则\(\{a_{n}\}\)的前\(5\)项和\(S_{5}=15\),其中正确的个数是\((\) \()\)