1*2+3*5+5*8+...+(2N-1)(3N

1*2+3*5+5*8+...+(2N-1)(3N-1)

1个回答

求证：1*2+2*5+3*8+…+n(3n-1)=n^2(n+1)
化简1/(2*5)+1/(5*8)+1/(8*11)+…+1/[（3n-1）*（3n+2）]=
1+3+5+.+(2n-5)+(2n-3)+(2n-1)+(2n+1)+(2n+3)
已知1*1+2*2+3*3+……+n*n=1/6n(n+1)(2n+1),求1*2+3*4+5*6+7*8+.+49*5
做个题lim[1/2×5 +1/5×8+1/8×11.+1/(3n-1)(3n+2) n→∞
1/1*3+1/3*5+1/5*7+.+1/（2n-1）(2n+1)=n/(2n+1)
1+2+3+4+5+6+7+8+9+…+n=n(n+1)/2 1+3+5+7+9+11+13+15+…+(2n-1)=n
求和：1/2+3/4+5/8+...+(2n-1)/2^n
求下列数列的极限：lim(n→∞) [1/(2*5)+1/(5*8)+1/(8*11)+……+1/(3n-1)*(3n+
1*2+2*3+3*4+4*5+5*6+6*7+…+n(n+1)=n(n+1)(n+2)/3