Isn't 5! = 120?
(I think you can click to enlarge it..)
Both the question and solution are highlighter.. But I Don't unnderstand.. My answer would be:
P5(x) = (x-1) + [(x2/2!)(x-1)2] + [(x3/3!)(X-1)3] + [(x4/4!)(X-1)4 + [(x5/5)(x-1)5
Where are all them zeros coming from, and where did the 120 come from D: !