$\"\"$

Statement : If $\"\"$ for all $\"\"$ in $\"\"$ , then $\"\"$ is decreasing on $\"\"$ .

The values of $\"\"$ are exist in the interval $\"\"$ where $\"\"$ .

Definition of derivatives is $\"\"$ .

$\"\"$

So the function is decreasing as $\"\"$ .

$\"\"$

If $\"\"$ for all $\"\"$ in $\"\"$ , then $\"\"$ is decreasing on $\"\"$ .