
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 $U=\mathbb{R}$, set $A=\left\{ x|1\leqslant x < 4 \right\}$, and set $B=\left\{ x|{x}^{2}+5ax+6{a}^{2}\leqslant 0 \right\}$,

(1) If $a=-1$, find $B\cap A$ and $B\cap {C}_{U}A$;

(2) If $A\cup B=A$ and $a < 0$, find the range of values for the real number $a$.

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