22. 已知函数f(x+2)=log3(3x+3−x)f(x+2)=\log _{3}(3^{x}+3^{-x})f(x+2)=log3(3x+3−x),若f(a−1)⩾f(2a+1)f(a-1)\geqslant f(2a+1)f(a−1)⩾f(2a+1)成立,则实数aaa的取值范围为((( )))