数学求数列通向公式如图
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数学求数列通向公式
如图
如图
a(n+1)/an = (n+2)/n
an/a(n-1) = (n+1)/(n-1)
a(n-1)/a(n-2) = n/(n-2)
...
a3/a2 = 4/2
a2/a1 = 3/1
所有相乘 a(n+1)/a1 = (n+2)(n+1)/2*1 = (n+2)(n+1)/2
所以 a(n+1) = (n+2)(n+1)/2
an = n(n+1)/2
an/a(n-1) = (n+1)/(n-1)
a(n-1)/a(n-2) = n/(n-2)
...
a3/a2 = 4/2
a2/a1 = 3/1
所有相乘 a(n+1)/a1 = (n+2)(n+1)/2*1 = (n+2)(n+1)/2
所以 a(n+1) = (n+2)(n+1)/2
an = n(n+1)/2