等比数列{an},a1=2,an+2a(n+1)+a(n+2)=0则S(2010)=?括号里的均为下标.
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等比数列{an},a1=2,an+2a(n+1)+a(n+2)=0则S(2010)=?括号里的均为下标.
![等比数列{an},a1=2,an+2a(n+1)+a(n+2)=0则S(2010)=?括号里的均为下标.](/uploads/image/z/19800273-57-3.jpg?t=%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%7Ban%7D%2Ca1%3D2%2Can%2B2a%28n%2B1%29%2Ba%28n%2B2%29%3D0%E5%88%99S%282010%29%3D%3F%E6%8B%AC%E5%8F%B7%E9%87%8C%E7%9A%84%E5%9D%87%E4%B8%BA%E4%B8%8B%E6%A0%87.)
等比数列{an},a1=2,an+2a(n+1)+a(n+2)=0,
an+2an *q+an *q²=0
1+2q+q²=0
q=-1
an=2*(-1)^(n-1)
S(2010)=2-2+2-2+.+2-2=0
an+2an *q+an *q²=0
1+2q+q²=0
q=-1
an=2*(-1)^(n-1)
S(2010)=2-2+2-2+.+2-2=0
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