求和:(a-1)+(a2-2)+…+(an-n),(a≠0)
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求和:(a-1)+(a2-2)+…+(an-n),(a≠0)
![求和:(a-1)+(a2-2)+…+(an-n),(a≠0)](/uploads/image/z/439890-42-0.jpg?t=%E6%B1%82%E5%92%8C%EF%BC%9A%EF%BC%88a-1%EF%BC%89%2B%EF%BC%88a2-2%EF%BC%89%2B%E2%80%A6%2B%EF%BC%88an-n%EF%BC%89%EF%BC%8C%EF%BC%88a%E2%89%A00%EF%BC%89)
原式=(a+a2+…+an)-(1+2+…+n)
=(a+a2+…+an)-
n(n+1)
2
=
a(1−an)
1−a−
n(n+1)
2,a≠1
n−n2
2,a=1
=(a+a2+…+an)-
n(n+1)
2
=
a(1−an)
1−a−
n(n+1)
2,a≠1
n−n2
2,a=1
求和:(a-1)+(a2-2)+…+(an-n),(a≠0)
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