
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
Find all values of the parameter \( b \) for which there exists a number \( a \) such that the system

$$
\left\{\begin{array}{l}
y = b - x^2, \\
x^2 + y^2 + 2 a^2 = 4 - 2 a (x + y)
\end{array}\right.
$$

has at least one solution \((x, y)\).

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