Answer
$(-\infty, 1] ∪ [2,\infty)$
Work Step by Step
For the domain of square root functions, the expression under the root must be greater than or equal to zero.
$x^2-3x+2\geq 0$
$(x-2)(x-1)\geq 0$
$x\leq1, x\geq2$ [the parabola concaves up, so values below 1 or above 2 are positive]
Therefore the domain of the function is: $(-\infty, 1] ∪ [2,\infty)$
