Answers
Answer:
ple calculation,
e−nn∑k=0nkk!=e−nn!n∑k=0(nk)nk(n−k)!(1)⋯=e−nn!n∑k=0(nk)nk∫∞0tn−ke−tdt=e−nn!∫∞0(n+t)ne−tdt(2)⋯=1n!∫∞ntne−tdt=1−1n!∫n0tne−tdt(3)⋯=1−√n(n/e)nn!∫√n0(1−u√n)ne√nudu.
We remark that
In (1), we utilized the famous formula n!=∫∞0tne−tdt.In (2), the substitution t+n↦t is used.In (3), the substitution t=n−√nu is used.
Then in view of the Stirling's formula, it suffices to show that
∫√n0(1−u√n)n
Answer:
∫√n0(1−u√n)n
Step-by-step explanation:
ple calculation,
e−nn∑k=0nkk!=e−nn!n∑k=0(nk)nk(n−k)!(1)⋯=e−nn!n∑k=0(nk)nk∫∞0tn−ke−tdt=e−nn!∫∞0(n+t)ne−tdt(2)⋯=1n!∫∞ntne−tdt=1−1n!∫n0tne−tdt(3)⋯=1−√n(n/e)nn!∫√n0(1−u√n)ne√nudu.
We remark that
In (1), we utilized the famous formula n!=∫∞0tne−tdt.In (2), the substitution t+n↦t is used.In (3), the substitution t=n−√nu is used.
Then in view of the Stirling's formula, it suffices to show that
∫√n0(1−u√n)n