What is $\sum\ln{(x_i!)}$?

Question

I started learning statistics and in my homework i should find the Maximum Likelihood Estimate. The function is $f_x(x)=e^{-\lambda n}\prod_{i=1}^n \frac{\lambda^{x_i}}{x_i!}$

Now i take the log-likelihood:
$$\ln{e^{-\lambda n}}+ln\prod_{i=1}^n \frac{\lambda^{x_i}}{x_i!}= -\lambda n +\sum_{i=1}^n (\ln{(\lambda^{x_i})}-\ln{(x_i!)})= -\lambda n+\sum_{i=1}^n \ln{(\lambda^{x_i})}-\sum_{i=1}^n \ln{(x_i!)}$$

The problem is now that i don't know what $\sum\ln{(x_i!)}$ is. Can someone help me here ?

Answer 1

By @roger $∑ln(xi!)$ doesn't matter, you have to maximize wrt λ