1. [5 pts] f(n) satisfies the recurrence equation n+1f(n)=nf(n1)+n+11 with f(1)=(1), give a Big- notation for f(n). Hint: Let an=n+1f(n), then an=an1+n+11 with a1=2f(1)=(1). Then an=n+11+n1++31+a1=(lnn),andf(n)=(n+1)an