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The domain of this function is the set of all real numbers x, where the expression under the square root is not negative
x^2 + 10x + 24 >= 0.
Factor left side
(x+6)*(x+4) >= 0.
The roots are -6 and -4.
Quadratic function x^2 + 10x + 24 is non-negative on the set
(-oo,-6] U [-4,oo).
ANSWER. The domain of the given function is the set of real numbers (-oo,-6] U [-4,oo).
Solved.