bn=2(1-a1)(1-a2)……(1-an) bn=?(表达式)bn、a1、an后面那个数是下标 - =an=1/(n+1)*(n+1)(n=1,2,3点点点点点点)b1=2(1-a1)b2=2(1-a1)(1-a2)一道一模一样的题,也是我问的,上面有40悬赏,咱穷 - =
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![bn=2(1-a1)(1-a2)……(1-an) bn=?(表达式)bn、a1、an后面那个数是下标 - =an=1/(n+1)*(n+1)(n=1,2,3点点点点点点)b1=2(1-a1)b2=2(1-a1)(1-a2)一道一模一样的题,也是我问的,上面有40悬赏,咱穷 - =](/uploads/image/z/12893555-11-5.jpg?t=bn%3D2%281-a1%29%281-a2%29%E2%80%A6%E2%80%A6%281-an%29+bn%3D%3F%28%E8%A1%A8%E8%BE%BE%E5%BC%8F%29bn%E3%80%81a1%E3%80%81an%E5%90%8E%E9%9D%A2%E9%82%A3%E4%B8%AA%E6%95%B0%E6%98%AF%E4%B8%8B%E6%A0%87+-+%3Dan%3D1%2F%28n%2B1%29%2A%28n%2B1%29%28n%3D1%2C2%2C3%E7%82%B9%E7%82%B9%E7%82%B9%E7%82%B9%E7%82%B9%E7%82%B9%29b1%3D2%281-a1%29b2%3D2%281-a1%29%281-a2%29%E4%B8%80%E9%81%93%E4%B8%80%E6%A8%A1%E4%B8%80%E6%A0%B7%E7%9A%84%E9%A2%98%EF%BC%8C%E4%B9%9F%E6%98%AF%E6%88%91%E9%97%AE%E7%9A%84%EF%BC%8C%E4%B8%8A%E9%9D%A2%E6%9C%8940%E6%82%AC%E8%B5%8F%EF%BC%8C%E5%92%B1%E7%A9%B7+-+%3D)
bn=2(1-a1)(1-a2)……(1-an) bn=?(表达式)bn、a1、an后面那个数是下标 - =an=1/(n+1)*(n+1)(n=1,2,3点点点点点点)b1=2(1-a1)b2=2(1-a1)(1-a2)一道一模一样的题,也是我问的,上面有40悬赏,咱穷 - =
bn=2(1-a1)(1-a2)……(1-an) bn=?(表达式)
bn、a1、an后面那个数是下标 - =
an=1/(n+1)*(n+1)(n=1,2,3点点点点点点)
b1=2(1-a1)
b2=2(1-a1)(1-a2)
一道一模一样的题,也是我问的,上面有40悬赏,咱穷 - =
bn=2(1-a1)(1-a2)……(1-an) bn=?(表达式)bn、a1、an后面那个数是下标 - =an=1/(n+1)*(n+1)(n=1,2,3点点点点点点)b1=2(1-a1)b2=2(1-a1)(1-a2)一道一模一样的题,也是我问的,上面有40悬赏,咱穷 - =
∵ an=1/(n+1)^2
∴1-an=1-1/(n+1)^2=n(n+2)/(n+1)^2=n/(n+1) * (n+2)/(n+1)
bn=2(1-a1)(1-a2)……(1-an)
=2×(1/2×3/2)×(2/3×4/3)×.×[(n-1)/n×(n+1)/n]×[n/(n+1)×(n+2)/(n+1)]
=(2×1/2)×(3/2×2/3)×(4/3×3/4)×.×[(n+1)/n×n/(n+1)]×(n+2)/(n+1)
=1×1×1×.×1×(n+2)/(n+1)
=(n+2)/(n+1)
1-an=1-1/(n+1)^2=n(n+2)/(n+1)^2
bn=2(1-a1)(1-a2)……(1-an)
=2(1×3/2^2)(2×4/3^3)(3×5/4^4)……[n(n+2)/(n+1)^2]
=2(1/2)(3/2)(2/3)(4/3)(3/4)(5/4)……[n/(n+1)][(n+2)/(n+1)]
=(n+2)/(n+1)
我把下标打在[]里 1-a[n]=(n(n+2))/((n+1)(n+1)) b[1],b[2]得死算一下 当n>=3时,b[n]=(n+2)/(2n+2)(过程见图片)
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