求lim(n→∞)[(1^3+4^3+7^3+……

求lim(n→∞)[(1^3+4^3+7^3+……+(3n-2)^3]/{[1+4+7+……+(3n-2)]^2}

1个回答

4/(1*2*3)+7/(2*3*4)+.+(3n+1)/[n(n+1)(n+2)]
lim（1/n^2+4/n^2+7/n^2+……+（3n-2）/n^2)
Tn=4*2^1+7*2^2.(3n+1)*2^n 2Tn=4*2^2+7*2^3.(3n-2)*2^n+(3n+1)*
1+4+7+...+3n-2=n(1+3n-2)/2
1+4+7+…+(3n+1)=(n+1)(3n+2)/2
lim(n→∞)[(2+3)/4+(2^2+3^2)/4^2+……+(2^n+3^n)/4^n]=lim(n→∞){[(
lim(2/2*3*4+2/3*4*5+...2/(n+1)(n+2)(n+3)) n→oo
lim [1*2+2*3+3*4+...+n*(n+1)]/n^3之值
1*2+2*3+3*4+4*5+5*6+6*7+…+n(n+1)=n(n+1)(n+2)/3
求（1）lim2n^2-n+1/n2^+3n （2）limx^2+2x/x^2+4x+1 （3）lim(1/1+x-3/