问题标题:
【设数列an,bn分别满足a1*a2*a3...*an=1*2*3*4...*n,b1+b2+b3+...bn=an^2,n属于N+a1*a2*a3...*an=1*2*3*4...*n,b1+b2+b3+...bn=an^2,n属于N+1)求数列an和bn的通项公式】
问题描述:
设数列an,bn分别满足a1*a2*a3...*an=1*2*3*4...*n,b1+b2+b3+...bn=an^2,n属于N+
a1*a2*a3...*an=1*2*3*4...*n,b1+b2+b3+...bn=an^2,n属于N+
1)求数列an和bn的通项公式
陶少国回答:
a1*a2*a3...*an*a(n+1)=1*2*3*4...*n*(n+1)
a1*a2*a3...*an=1*2*3*4...*n
两式相除
=>a1=1,a(n+1)=n+1=>an=n
b1+b2+b3+...bn=an^2=n^2
b1+b2+b3+...bn+b(n+1)=a(n+1)^2=(n+1)^2
两式相减
=>b1=1,b(n+1)=(n+1)^2-n^2=2n+1
=>bn=2n-1
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