1/0!n!+1/1!(n-1)!+1/2!（n-2）!+...+1/n!0!=求解答过程!

Question

1/0!n!+1/1!(n-1)!+1/2!（n-2）!+...+1/n!0!=________求解答过程!

Answer 1

n!/0!n!+n!/1!(n-1)!++...+n!/n!0!
=Cn(0)+Cn(1)+……+Cn(n)
=2^n
所以原式=2^n/n!