Question

求下列数列极限，请列出详细过程： lim下面n→∞　[1/1×2×3+1/2×3×4+...+1/(n-1)n(n+1)]

图怎么就不显示呢

Answer 1

1/1×2×3+1/2×3×4+...+1/(n-1)n(n+1)
=1/2×[1/1×2-1/2×3+1/2×3-1/3×4+……+1/(n-1)n-1/n(n+1)]
=1/2×[1/1×2-1/n(n+1)]
n→∞则1/n(n+1)→0
所以原式=1/2×1/1×2=1/4

Answer 2

放大不就可以了