Question

限界受験生

この和Sを求めてください。お願いしますm(_ _)m

1 = 3 (
1+2+1+²+3
3htl
(2) S=1+1+2
+
cl
3htl
1
1+2+3 + ......+n
3h+l
+
(+-1

Answer 1

✨ Best Answer ✨

Nn_nt

分母=1+2+3+…n=nΣk=1(1/2k(k+1))
nΣk=1(1/1/2k(k+1))
2nΣk=1(1/k(k+1))
2nΣk=1(1/k-(1/k+1))
部分和
2×((1-1/2)+…(1/n-(1/n+1)))
2×(1-1/n+1)
2×n/n+1
=2n/n+1