等差数列-17,-15,-13,-11,.的m项和最小,则m=?
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等差数列-17,-15,-13,-11,.的m项和最小,则m=?
等差数列-17,-15,-13,-11,.的m项和最小,则m=?
等差数列-17,-15,-13,-11,.的m项和最小,则m=?
an=2n-19
设前m项和最小,则有am0
解得8.5
-17,-15,-13,-11,-9,-7,-5,-3,-1,、、、第九项是相加和最小,所以m=9