已知数列﹛an﹜满足an+1=an+n,﹙n+1)为下标,且a58=2007,则a1=

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已知数列﹛an﹜满足an+1=an+n,﹙n+1)为下标,且a58=2007,则a1=
已知数列﹛an﹜满足an+1=an+n,﹙n+1)为下标,且a58=2007,则a1=

已知数列﹛an﹜满足an+1=an+n,﹙n+1)为下标,且a58=2007,则a1=
a58=a1+1+2+3+……+57=2007
a1+(1+57)×57÷2=2007
a1=354

a(n+1)=an+n
a(n+1)-an = n
a(n)- a1 = (n-1)+...+1
= n(n-1)/2
put n=58
a58-a1= 58(57)/2
2007-a1=1653
a1=354a(n)- a1 = n+(n-1)+...+2 = (n+2)(n-1)...

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a(n+1)=an+n
a(n+1)-an = n
a(n)- a1 = (n-1)+...+1
= n(n-1)/2
put n=58
a58-a1= 58(57)/2
2007-a1=1653
a1=354

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