
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
A moving circle is externally tangent to a known circle $O_1: (x+3)^2+y^2=1$ and internally tangent to another circle $O_2: (x-3)^2+y^2=81$. Find the equation of the trajectory of the center $M$ of the moving circle.

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