9.
设数列\(\{{{a}_{n}}\}\)的前\(n\)项和为\({S}_{n} (n∈{N}^{*}) \),关于数列\(\{{{a}_{n}}\}\)有下列四种命题:
\(①\)若\(\{{{a}_{n}}\}\)既是等差数列又是等比数列,则\({a}_{n}={a}_{n-1}\neq 0 (g(x)=f(x)-k)\);
\(②\)若\({S}_{n}=a{n}^{2}+bn(a,b∈R) \)则\(\{{{a}_{n}}\}\)是等差数列;
\(③\)若\({S}_{n}=1-(-1{)}^{n} \),则\(\{{{a}_{n}}\}\)是等比数列;
\(④\)若数列\(\{{{a}_{n}}\}\)是等比数列,则\({S}_{m},{S}_{2m}-{S}_{m},{S}_{3m}-{S}_{2m}(m∈{N}^{*}) \)也成等比数列.
其中正确的命题是 \(.(\)填序号\()\)