Question
The domain of the function $$\sqrt {{x^2} - 5x + 6} + \sqrt {2x + 8 - {x^2}} $$ is :
A.
$$\left[ {2,\,3} \right]$$
B.
$$\left[ { - 2,\,4} \right]$$
C.
$$\left[ { - 2,\,2} \right] \cup \left[ {3,\,4} \right]$$
D.
$$\left[ { - 2,\,1} \right] \cup \left[ {2,\,4} \right]$$
Answer :
$$\left[ { - 2,\,2} \right] \cup \left[ {3,\,4} \right]$$
Solution :
$$f\left( x \right) = \sqrt {\left( {x - 2} \right)\left( {x - 3} \right)} + \sqrt { - \left( {x - 4} \right)\left( {x + 2} \right)} $$
The first part is real outside $$\left( {2,\,3} \right)$$ and the second is real in $$\left[ { - 2,\,4} \right]$$ so that the domain is $$\left[ { - 2,\,2} \right] \cup \left[ {3,\,4} \right].$$