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Which of the following is the domain of the function:

$$ f(x)=-\sqrt { 2-x } +1 $$

$ \{ x:x<2\} $

$ \{ x:x\le 2\} $

$ \{ x:x>2\} $

$ \{ x:x\ge 2\} $

$ \{ x:x\neq 2\} $