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数学
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等差数列an的项公式为an=2-3n,则它的公差d=
人气:447 ℃ 时间:2020-04-08 19:52:08
解答
an=2-3n
a(n-1)=2-3(n-1)
=2-3n+3
=5-3n
d=an-a(n-1)=2-3n-(5-3n)
=2-3n-5+3n
=-3
所以公差d=-3
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