The domain of a(x) here is all real numbers x, or (–∞, ∞).
The domain of b(x) is [4, ∞).
The square-root function is defined when the radicand is greater than OR equal to zero, so we write [tex]x-4 \geq 0[/tex], being careful to include zero. [tex]x \geq 4[/tex].
These two domains overlap for [4, ∞).
The domain is [4, ∞)