已知等差数列的前n项和Sn=a•2^(n+1)+1/8,则a的值为____请详细讲解
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![已知等差数列的前n项和Sn=a•2^(n+1)+1/8,则a的值为____请详细讲解](/uploads/image/z/10224218-2-8.jpg?t=%E5%B7%B2%E7%9F%A5%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8CSn%3Da%26%238226%3B2%5E%28n%2B1%29%2B1%2F8%2C%E5%88%99a%E7%9A%84%E5%80%BC%E4%B8%BA____%E8%AF%B7%E8%AF%A6%E7%BB%86%E8%AE%B2%E8%A7%A3)
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已知等差数列的前n项和Sn=a•2^(n+1)+1/8,则a的值为____请详细讲解
已知等差数列的前n项和Sn=a•2^(n+1)+1/8,则a的值为____
请详细讲解
已知等差数列的前n项和Sn=a•2^(n+1)+1/8,则a的值为____请详细讲解
Sn=a•2^(n+1)+1/8
n=1
a1 = 4a+1/8
n=2
a1+a2 = 8a +1/8
a2 = 4a
n=3
a1+a2+a3 = 16a+1/8
a3 = 8a
a3-a2 = a2-a1
8a-4a= 4a -(4a+1/8)
4a= -1/8
a = -1/32