
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given the function $f(x)=\ln(ax+1)+ \dfrac {1-x}{1+x}$, where $a > 0$.  
$(1)$ If $f(x)$ attains an extremum at $x=1$, find the value of $a$;  
$(2)$ If the minimum value of $f(x)$ is $1$, find the range of $a$.

Present the answer in LaTex format: \boxed{Your answer}
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