
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 that the domain of the even function $f(x)$ is $R$, and for any $x_{1}$, $x_{2}\in \left(-\infty ,0\right](x_{1}\neq x_{2})$, $\frac{f(x_2)-f(x_1)}{x_2-x_1}＜0$ holds, find the range of real number $a$ such that $f(1-a) > f(2a-1)$.

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