
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 set $A=\{y|y=-2^x, x\in[2,3]\}$, $B=\{x|x^2+3x-a^2-3a>0\}$.
1. When $a=4$, find $A\cap B$;
2. If the proposition "x∈A" is a sufficient but not necessary condition for the proposition "x∈B", find the range of the real number $a$.

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