Find the MLE for ? Solution 2. Relevant equations PX(x) = e^-lambda.lambda^x/x! E(X) = lambda ??? or mean var (X) = lambda ?? or mean 3. The attempt at a solution I am really struggling with stats, hope someone can help. I try to find likelihood function L(x1,x2,...,xn|lambda) = e^- lambda.lambda^x/x! = capital pi from i=1 to n, e^-lambda.lambda^xi/xi! then I\'m stuck. Differentiating with respect to lambda, -e^-lambda.xlambda^(x-1)/x!.