lim(rad n2+n+1 -1-n)= lim(n2+n+1 - n2-2n+1)/(rad n2+n+1 +1+n) dupa rationalizarea numaratorului
lim(-n)/(rad n2+n+1 +1+n)
lim(-n)/n(rad 1+1/n+1/n2 +1/n +1) am scos factor fortat n2 sub radical si n la numitor
lim(-1)/(rad 1+1/n+1/n2 +1/n +1)
trecem la limita
-1/(rad 1+0+0 +0+1)=-1/2
