
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 algebraic expression $(2x^2 + ax - y + 6) - (2bx^2 - 3x + 5y - 1)$.  
(1) When $a=$____, $b=$____, the value of this algebraic expression is independent of the value of $x$.  
(2) Under the condition of (1), the value of the polynomial $3(a^2 - 2ab - b^2) - (4a^2 + ab + b^2)$ is ____.

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