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).