$\"\"$

The function is $\"\"$ .

Find the value of $\"\"$ .

The graph of the function contains the point $\"\"$ .

Therefore, the function is $\"\"$ .

Definition of logarithmic functions $\"y$ if and only if $\"x$ .

$\"\"$

The value of the logarithmic function always be positive.

Therefore, $\"\"$ .

$\"\"$

The value of $\"\"$ is $\"\"$ .