An=2*3^n-1+(a-3)2^n-2

zjlyxl2022-10-04 11:39:541条回答

An=2*3^n-1+(a-3)2^n-2
那么A(n+1)-An=4*3^n-1+(a-3)2^n-2

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jakeyxun 共回答了14个问题 | 采纳率85.7%
a(n+1) = 2*3^n + (a-3)2^(n-1)
a(n) = 2*3^(n-1) + (a-3)2^(n-2)
a(n+1)-a(n)
= 2*(3^n - 3^(n-1)) + (a-3)(2^(n-1) - 2^(n-2))
= 2*3^(n-1)*(3-1) + (a-3)*2^(n-2)*(2-1)
= 4*3^(n-1) + (a-3)*2^(n-2)
所以,是的.
1年前

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