为什么lim(n→∞)n/(3n-1)=1/3

求lim n→∞ (1+2/n)^n+3 lim(n→∞)[1/(3n+1)+1/(3n+2)+~1/(3n+n)] 求极限lim [ 2^(n+1)+3^(n+1)]/2^n+3^n (n→∞) lim n →∞ (1^n+3^n+2^n)^1/n,求数列极限 求极限lim(x→∞)（1/n+2/n+3/n..+n/n） 求极限：lim(n→∞)[（3n+1 ）/（3n+2）]^(n+1) 求极限lim(-2)^n+3^n/(-2)^[n+1]+3^[n+1] (x→∞) 求极限lim(n→∞)(3n^2-n+1)/(2+n^2)? lim(x→∞）1+2+3+…+n/(n+2)(n+4)=? lim[(n+3)/(n+1))]^(n-2) 【n无穷大】 一道极限题,lim[n^2(2n+1)]/(n^3+n+4)n->∞ lim (n→∞) (n^2/(an+b)-n^3/(2n^2-1))=1/4 求a,b