$\"\"$

\

Original function is $\"\"$ .

\

Replace $\"\"$ in original function.

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Product of two difference sings is negative.

\

$\"\"$

\

$\"\"$

\

$\"\"$ $\"\"$

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Replace x = 4 in original function.

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ $\"\"$ $\"\"$ and $\"\"$ .