Domain of √(5|x|−x²−6)

Find the Domain of the Function

Question:

The domain of the function

\[ f(x)=\sqrt{5|x|-x^2-6} \]

is

(a) \(( -3,-2)\cup(2,3)\)
(b) \([ -3,-2]\cup[2,3)\)
(c) \([ -3,-2]\cup[2,3]\)
(d) none of these

Solution:

For square root function,

\[ 5|x|-x^2-6\ge0 \]

Case I: \(x\ge0\)

\[ 5x-x^2-6\ge0 \]

\[ x^2-5x+6\le0 \]

\[ (x-2)(x-3)\le0 \]

\[ 2\le x\le3 \]

Case II: \(x<0\)

\[ -5x-x^2-6\ge0 \]

\[ x^2+5x+6\le0 \]

\[ (x+2)(x+3)\le0 \]

\[ -3\le x\le-2 \]

Therefore,

\[ \boxed{[-3,-2]\cup[2,3]} \]

\[ \boxed{\text{Correct Answer: (c)}} \]

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