\(f : x \to \sqrt{4 -2x}\) defined on the set of real numbers, R, which has range from \((-\infty, \infty)\) but because of the root sign, it is defined from \([0, \infty)\). 

This is because the root of numbers only has real number values from 0 and upwards.

\(\sqrt{4-2x} \geq 0 \implies 4-2x \geq 0\)

\(-2x \geq -4; x \leq 2\)