Answer:
[tex]x\ge3[/tex]
Step-by-step explanation:
The given function is [tex]f(x)=\sqrt{x-3}[/tex].
The domain of this function refers to all values of x, for which the function is defined.
This square root function is defined when the expression under the radical sign is greater or equal to zero.
That is; the domain of the function is [tex]x-3\ge0[/tex]
This implies that [tex]x\ge3[/tex]
