
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 planar vectors $\overrightarrow {a}$ and $\overrightarrow {b}$ with an angle of $\frac {2π}{3}$ between them, and $|\overrightarrow {a}|=3, |\overrightarrow {b}|=2$, calculate the value of $\overrightarrow {a}\cdot (\overrightarrow {a}-2\overrightarrow {b})$.

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