已知数列{an}满足a1=1且（n+2）a下标n+1=n下标an则a10的值是
问题描述：
已知数列{an}满足a1=1且（n+2）a下标n+1=n下标an则a10的值是
答
a(n+1) / a(n) = n / (n+1)
a(n) / a(n-1)= (n-1) / n
a(n-1)/ a(n-2)= (n-2)/(n-1)
...
a3 / a2 = 2 / 3
a2 / a1 = 1 / 2
累乘：
a(n) / a1 = 1 / n
a(n) = 1 / n
a10 = 1/10正确的答案是1/55.....a(n+1) / a(n) = n / (n+2)a(n) / a(n-1)= (n-1) / (n+1)a(n-1)/ a(n-2)= (n-2) / na(n-2)/ a(n-3)= (n-3) / (n-1)a(n-3)/ a(n-4)= (n-4) / (n-2)...a5 / a4 = 4 / 6a4 / a3 = 3 / 5a3 / a2 = 2 / 4a2 / a1 = 1 / 3累乘：(隔项相消)a(n) / a1 = 2 / n(n+1)a(n) = 2 / n(n+1)a10 = 1/55方法都一样......谢谢您！！！