Question

なつ

想請問是怎麼變成3/2n(n+1)的

1+1=3=3x1
+
Az=A++3x2
√3 = x+3×3
094=243+3x4
An = Anx+3n
³n
An = 3 × (1+2+3+.+n) = ≤ n (n+1)
+1

Answer 1

✨ 最佳解答 ✨

綾

1 + 2 + 3 + … + n = n(n+1)/2

證明是
S = 1 + 2 + 3 + … + n
S = n + (n-1) + (n-2) + … + 1
兩式相加
2S = (1+n) + (2+n-1) + … + (n+1)
括號內每一組都是n+1、總共有n組
故2S = n(n+1)
S = n(n+1)/2

なつ

謝謝您🙏🏻