In the expression
I.
a.Where is the
+1 coming from?
b.I am assuming they are using the coefficient from
c.If this is correct then why does the +1 get grouped within

resulting in

, rather staying on the outside of the brackets? e.g.
II.
And if thats the case why are they not using a +1 in the second term as well?
Many Thanks for clarification!