
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 universal set $U=\{x|-5\leqslant x\leqslant 3\}$, $A=\{x|-5\leqslant x < -1\}$, $B=\{x|-1\leqslant x < 1\}$,  
(1) Find ${{C}_{U}}A$, $A\cap({{C}_{U}}B)$;  
(2) If $C=\{x|1-a\leqslant x\leqslant 2a+1\}$, and $C\subseteq A$, find the range of the real number $a$.

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